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• Engine Rendering pipeline : Making shaders generic

  - by fakhir

  I am trying to make a 2D game engine using OpenGL ES 2.0 (iOS for now). I've written Application layer in Objective C and a separate self contained RendererGLES20 in C++. No GL specific call is made outside the renderer. It is working perfectly. But I have some design issues when using shaders. Each shader has its own unique attributes and uniforms that need to be set just before the main draw call (glDrawArrays in this case). For instance, in order to draw some geometry I would do: void RendererGLES20::render(Model * model) { // Set a bunch of uniforms glUniformMatrix4fv(.......); // Enable specific attributes, can be many glEnableVertexAttribArray(......); // Set a bunch of vertex attribute pointers: glVertexAttribPointer(positionSlot, 2, GL_FLOAT, GL_FALSE, stride, m->pCoords); // Now actually Draw the geometry glDrawArrays(GL_TRIANGLES, 0, m->vertexCount); // After drawing, disable any vertex attributes: glDisableVertexAttribArray(.......); } As you can see this code is extremely rigid. If I were to use another shader, say ripple effect, i would be needing to pass extra uniforms, vertex attribs etc. In other words I would have to change the RendererGLES20 render source code just to incorporate the new shader. Is there any way to make the shader object totally generic? Like What if I just want to change the shader object and not worry about game source re-compiling? Any way to make the renderer agnostic of uniforms and attributes etc?. Even though we need to pass data to uniforms, what is the best place to do that? Model class? Is the model class aware of shader specific uniforms and attributes? Following shows Actor class: class Actor : public ISceneNode { ModelController * model; AIController * AI; }; Model controller class: class ModelController { class IShader * shader; int textureId; vec4 tint; float alpha; struct Vertex * vertexArray; }; Shader class just contains the shader object, compiling and linking sub-routines etc. In Game Logic class I am actually rendering the object: void GameLogic::update(float dt) { IRenderer * renderer = g_application->GetRenderer(); Actor * a = GetActor(id); renderer->render(a->model); } Please note that even though Actor extends ISceneNode, I haven't started implementing SceneGraph yet. I will do that as soon as I resolve this issue. Any ideas how to improve this? Related design patterns etc? Thank you for reading the question.

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• Do you have to be good at math to be a good programmer?

  - by Charles Roper

  It seems that conventional wisdom suggests that good programmers are also good at math. Or that the two are somehow intrinsically linked. Many programming books I have read provide many examples that are solutions to math problems, or are somehow related to math as if these examples are what make sense to most people. So the question I would like to float is: do you have to be good at math to be a good programmer?

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• Silverlight IConvertible TypeConverter

  - by codingbloke

  I recently answered the following question on stackoverflow:  Silverlight 3 custom control: only ‘int’ as numeric type for a property? [e.g. long or int64 seems to break] I quickly knocked up the class ConvertibleTypeConverter<T> that I posted in the question (listed later here as well). Afterward I fully expected to find that of the usual clever “bods who blog” to have covered this probably with a better solution than I.  So far though I’ve not found one so I thought I’d blog it myself. The Problem Here is a classic gotcha I’ve seen asked more than once on stackoverflow :- public class MyClass {     public float SomeValue { get; set; } } <local:MyClass SomeValue="45.15" /> This fails with the error  “Failed to create a 'System.Single' from the text '45.15'”  and results in much premature hair loss.  Fortunately this is SL4, in SL3 the error message is almost meaningless.  So what gives, how can it be that this fails when we can see other very similar values parsing happily all over the place? It comes down the fact that the Xaml parser only handles a few of the primitive data types namely: bool, int, string and double.  Since the parser has no idea how to convert a string to a float we get the above error. The Solution The sensible solution is “use double not float” but lets not dwell on that, there has to be occasions where such an answer isn’t acceptable. In order to achieve parsing of other types we need an implementation of TypeConverter for the type of the property and then we need to use the TypeConverterAttribute to decorate the property .  As an example the Silverlight SDK provides one for DateTime the DateTimeTypeConverter (yes I know DateTime isn’t really a primitive). The following class will parse in Xaml:- public class MyClass {     [TypeConverter(typeof(DateTimeTypeConverter))]     public DateTime SomeValue {get; set; } } So far though we would need to create a TypeConverter for each primitive type we are using, what if I had the following mad class to support in Xaml:- public class StrangePrimitives {     public Boolean BooleanProp { get; set; }     public Byte ByteProp { get; set; }     public Char CharProp { get; set; }     public DateTime DateTimeProp { get; set; }     public Decimal DecimalProp { get; set; }     public Double DoubleProp { get; set; }     public Int16 Int16Prop { get; set; }     public Int32 Int32Prop { get; set; }     public Int64 Int64Prop { get; set; }     public SByte SByteProp { get; set; }     public Single SingleProp { get; set; }     public String StringProp { get; set; }     public UInt16 UInt16Prop { get; set; }     public UInt32 UInt32Prop { get; set; }     public UInt64 UInt64Prop { get; set; } } Then I want to fill an instance of StrangePrimitives with the following Xaml which of course fails. <local:StrangePrimitives x:Key="MyStrangePrimitives"                          BooleanProp="True"                          ByteProp="156"                          CharProp="A"                          DateTimeProp="06 Jun 2010"                          DecimalProp="123.56"                          DoubleProp="8372.937803"                          Int16Prop="16532"                          Int32Prop="73738248"                          Int64Prop="12345678909298"                          SByteProp="-123"                          SingleProp="39.0"                          StringProp="Hello, World!"                          UInt16Prop="40000"                          UInt32Prop="4294967295"                          UInt64Prop="18446744073709551615"      /> I got to thinking, though, one thing all these primitive types have in common is that they all implement IConvertible so it should be possible to write just one converter to handle them all.  Here it is:- The ConvertibleTypeConverter public class ConvertibleTypeConverter<T> : TypeConverter where T : IConvertible {     public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)     {         return sourceType.GetInterface("IConvertible", false) != null;     }     public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)     {         return destinationType.GetInterface("IConvertible", false) != null;     }     public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)     {         return ((IConvertible)value).ToType(typeof(T), culture);     }     public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType)     {         return ((IConvertible)value).ToType(destinationType, culture);     } } I won’t bore you with an explanation of how it works, it simply adapts one existing interface (the IConvertible) and exposes it as another (the TypeConverter).   With that in place the previous strange primitives class can be modified as:- public class StrangePrimitives {     public Boolean BooleanProp { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<Byte>))]     public Byte ByteProp { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<Char>))]     public Char CharProp { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<DateTime>))]     public DateTime DateTimeProp { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<Decimal>))]     public Decimal DecimalProp { get; set; }     public Double DoubleProp {get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<Int16>))]     public Int16 Int16Prop { get; set; }     public Int32 Int32Prop { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<Int64>))]     public Int64 Int64Prop { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<SByte>))]     public SByte SByteProp { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<Single>))]     public Single SingleProp { get; set; }     public String StringProp { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<UInt16>))]     public UInt16 UInt16Prop { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<UInt32>))]     public UInt32 UInt32Prop { get; set; }     [TypeConverter(typeof(ConvertibleTypeConverter<UInt64>))]     public UInt64 UInt64Prop { get; set; } } This results in the previous Xaml parsing happily.  Now it seems such an obvious thing to do that one may wonder why such a class doesn’t already existing in Silverlight or at least in the SDK.   I would not be surprised if there were some very good reasons hence use the ConvertibleTypeConverter with caution.  It does seem to me to be a useful little class to have lying around in the toolbox for the odd occasion where it may be needed.

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• I need to move an entity to the mouse location after i rightclick

  - by I.Hristov

  Well I've read the related questions-answers but still cant find a way to move my champion to the mouse position after a right-button mouse-click. I use this code at the top: float speed = (float)1/3; And this is in my void Update: //check if right mouse button is clicked if (mouse.RightButton == ButtonState.Released && previousButtonState == ButtonState.Pressed) { // gets the position of the mouse in mousePosition mousePosition = new Vector2(mouse.X, mouse.Y); //gets the current position of champion (the drawRectangle) currentChampionPosition = new Vector2(drawRectangle.X, drawRectangle.Y); // move champion to mouse position: //handles the case when the mouse position is really close to current position if (Math.Abs(currentChampionPosition.X - mousePosition.X) <= speed && Math.Abs(currentChampionPosition.Y - mousePosition.Y) <= speed) { drawRectangle.X = (int)mousePosition.X; drawRectangle.Y = (int)mousePosition.Y; } else if (currentChampionPosition != mousePosition) { drawRectangle.X += (int)((mousePosition.X - currentChampionPosition.X) * speed); drawRectangle.Y += (int)((mousePosition.Y - currentChampionPosition.Y) * speed); } } previousButtonState = mouse.RightButton; What that code does at the moment is on a click it brings the sprite 1/3 of the distance to the mouse but only once. How do I make it move consistently all the time? It seems I am not updating the sprite at all. EDIT I added the Vector2 as Nick said and with speed changed to 50 it should be OK. I tried it with if ButtonState.Pressed and it works while pressing the button. Thanks. However I wanted it to start moving when single mouse clicked. It should be moving until reaches the mousePosition. The Edit of Nick's post says to create another Vector2, But I already have the one called mousePosition. Not sure how to use another one. //gets a Vector2 direction to move *by Nick Wilson Vector2 direction = mousePosition - currentChampionPosition; //make the direction vector a unit vector direction.Normalize(); //multiply with speed (number of pixels) direction *= speed; // move champion to mouse position if (currentChampionPosition != mousePosition) { drawRectangle.X += (int)(direction.X); drawRectangle.Y += (int)(direction.Y); } } previousButtonState = mouse.RightButton;

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• Refactoring an ERB Template to Haml

  - by Liam McLennan

  ERB is the default view templating system used by Ruby on Rails. Haml is an alternative templating system that uses whitespace to represent document structure. The example from the haml website shows the following equivalent markup: Haml ERB #profile .left.column #date= print_date #address= current_user.address .right.column #email= current_user.email #bio= current_user.bio <div id="profile"> <div class="left column"> <div id="date"><%= print_date %></div> <div id="address"><%= current_user.address %></div> </div> <div class="right column"> <div id="email"><%= current_user.email %></div> <div id="bio"><%= current_user.bio %></div> </div> </div> I like haml because it is concise and the significant whitespace makes it easy to see the structure at a glance. This post is about a ruby project but nhaml makes haml available for asp.net MVC also. The ERB Template Today I spent some time refactoring an ERB template to Haml. The template is called list.html.erb and its purpose is to render a list of tweets (twitter messages). <style> form { float: left; } </style> <h1>Tweets</h1> <table> <thead><tr><th></th><th>System</th><th>Human</th><th></th></tr></thead> <% @tweets.each do |tweet| %> <tr> <td><%= h(tweet['text']) %></td> <td><%= h(tweet['system_classification']) %></td> <td><%= h(tweet['human_classification']) %></td> <td><form action="/tweet/rate" method="post"> <%= token_tag %> <input type="submit" value="Positive"/> <input type="hidden" value="<%= tweet['id']%>" name="id" /> <input type="hidden" value="positive" name="rating" /> </form> <form action="/tweet/rate" method="post"> <%= token_tag %> <input type="submit" value="Neutral"/> <input type="hidden" value="<%= tweet['id']%>" name="id" /> <input type="hidden" value="neutral" name="rating" /> </form> <form action="/tweet/rate" method="post"> <%= token_tag %> <input type="submit" value="Negative"/> <input type="hidden" value="<%= tweet['id']%>" name="id" /> <input type="hidden" value="negative" name="rating" /> </form> </td> </tr> <% end %> </table> Haml Template: Take 1 My first step was to convert this page to a Haml template in place. Directly translating the ERB template to Haml resulted in: list.haml %style form {float: left;} %h1 Tweets %table %thead %tr %th %th System %th Human %th %tbody - @tweets.each do |tweet| %tr %td= tweet['text'] %td= tweet['system_classification'] %td= tweet['human_classification'] %td %form{ :action=>"/tweet/rate", :method=>"post"} = token_tag <input type="submit" value="Positive"/> <input type="hidden" value="positive" name="rating" /> %input{ :type=>"hidden", :value => tweet['id']} %form{ :action=>"/tweet/rate", :method=>"post"} = token_tag <input type="submit" value="Neutral"/> <input type="hidden" value="neutral" name="rating" /> %input{ :type=>"hidden", :value => tweet['id']} %form{ :action=>"/tweet/rate", :method=>"post"} = token_tag <input type="submit" value="Negative"/> <input type="hidden" value="negative" name="rating" /> %input{ :type=>"hidden", :value => tweet['id']} end I like this better already but I can go further. Haml Template: Take 2 The haml documentation says to avoid using iterators so I introduced a partial template (_tweet.haml) as the template to render a single tweet. _tweet.haml %tr %td= tweet['text'] %td= tweet['system_classification'] %td= tweet['human_classification'] %td %form{ :action=>"/tweet/rate", :method=>"post"} = token_tag <input type="submit" value="Positive"/> <input type="hidden" value="positive" name="rating" /> %input{ :type=>"hidden", :value => tweet['id']} %form{ :action=>"/tweet/rate", :method=>"post"} = token_tag <input type="submit" value="Neutral"/> <input type="hidden" value="neutral" name="rating" /> %input{ :type=>"hidden", :value => tweet['id']} %form{ :action=>"/tweet/rate", :method=>"post"} = token_tag <input type="submit" value="Negative"/> <input type="hidden" value="negative" name="rating" /> %input{ :type=>"hidden", :value => tweet['id']} and the list template is simplified to: list.haml %style form {float: left;} %h1 Tweets %table     %thead         %tr             %th             %th System             %th Human             %th     %tbody         = render(:partial => "tweet", :collection => @tweets) That is definitely an improvement, but then I noticed that _tweet.haml contains three form tags that are nearly identical.   Haml Template: Take 3 My first attempt, later aborted, was to use a helper to remove the duplication. A much better solution is to use another partial.  _rate_button.haml %form{ :action=>"/tweet/rate", :method=>"post"} = token_tag %input{ :type => "submit", :value => rate_button[:rating].capitalize } %input{ :type => "hidden", :value => rate_button[:rating], :name => 'rating' } %input{ :type => "hidden", :value => rate_button[:id], :name => 'id' } and the tweet template is now simpler: _tweet.haml %tr %td= tweet['text'] %td= tweet['system_classification'] %td= tweet['human_classification'] %td = render( :partial => 'rate_button', :object => {:rating=>'positive', :id=> tweet['id']}) = render( :partial => 'rate_button', :object => {:rating=>'neutral', :id=> tweet['id']}) = render( :partial => 'rate_button', :object => {:rating=>'negative', :id=> tweet['id']}) list.haml remains unchanged. Summary I am extremely happy with the switch. No doubt there are further improvements that I can make, but I feel like what I have now is clean and well factored.

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• LWJGL - Mixing 2D and 3D

  - by nathan

  I'm trying to mix 2D and 3D using LWJGL. I have wrote 2D little method that allow me to easily switch between 2D and 3D. protected static void make2D() { glEnable(GL_BLEND); GL11.glMatrixMode(GL11.GL_PROJECTION); GL11.glLoadIdentity(); glOrtho(0.0f, SCREEN_WIDTH, SCREEN_HEIGHT, 0.0f, 0.0f, 1.0f); GL11.glMatrixMode(GL11.GL_MODELVIEW); GL11.glLoadIdentity(); } protected static void make3D() { glDisable(GL_BLEND); GL11.glMatrixMode(GL11.GL_PROJECTION); GL11.glLoadIdentity(); // Reset The Projection Matrix GLU.gluPerspective(45.0f, ((float) SCREEN_WIDTH / (float) SCREEN_HEIGHT), 0.1f, 100.0f); // Calculate The Aspect Ratio Of The Window GL11.glMatrixMode(GL11.GL_MODELVIEW); glLoadIdentity(); } The in my rendering code i would do something like: make2D(); //draw 2D stuffs here make3D(); //draw 3D stuffs here What i'm trying to do is to draw a 3D shape (in my case a quad) and i 2D image. I found this example and i took the code from TextureLoader, Texture and Sprite to load and render a 2D image. Here is how i load the image. TextureLoader loader = new TextureLoader(); Sprite s = new Sprite(loader, "player.png") And how i render it: make2D(); s.draw(0, 0); It works great. Here is how i render my quad: glTranslatef(0.0f, 0.0f, 30.0f); glScalef(12.0f, 9.0f, 1.0f); DrawUtils.drawQuad(); Once again, no problem, the quad is properly rendered. DrawUtils is a simple class i wrote containing utility method to draw primitives shapes. Now my problem is when i want to mix both of the above, loading/rendering the 2D image, rendering the quad. When i try to load my 2D image with the following: s = new Sprite(loader, "player.png); My quad is not rendered anymore (i'm not even trying to render the 2D image at this point). Only the fact of creating the texture create the issue. After looking a bit at the code of Sprite and TextureLoader i found that the problem appears after the call of the glTexImage2d. In the TextureLoader class: glTexImage2D(target, 0, dstPixelFormat, get2Fold(bufferedImage.getWidth()), get2Fold(bufferedImage.getHeight()), 0, srcPixelFormat, GL_UNSIGNED_BYTE, textureBuffer); Commenting this like make the problem disappear. My question is then why? Is there anything special to do after calling this function to do 3D? Does this function alter the render part, the projection matrix?

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• Ray Intersecting Plane Formula in C++/DirectX

  - by user4585

  I'm developing a picking system that will use rays that intersect volumes and I'm having trouble with ray intersection versus a plane. I was able to figure out spheres fairly easily, but planes are giving me trouble. I've tried to understand various sources and get hung up on some of the variables used within their explanations. Here is a snippet of my code: bool Picking() { D3DXVECTOR3 vec; D3DXVECTOR3 vRayDir; D3DXVECTOR3 vRayOrig; D3DXVECTOR3 vROO, vROD; // vect ray obj orig, vec ray obj dir D3DXMATRIX m; D3DXMATRIX mInverse; D3DXMATRIX worldMat; // Obtain project matrix D3DXMATRIX pMatProj = CDirectXRenderer::GetInstance()->Director()->Proj(); // Obtain mouse position D3DXVECTOR3 pos = CGUIManager::GetInstance()->GUIObjectList.front().pos; // Get window width & height float w = CDirectXRenderer::GetInstance()->GetWidth(); float h = CDirectXRenderer::GetInstance()->GetHeight(); // Transform vector from screen to 3D space vec.x = (((2.0f * pos.x) / w) - 1.0f) / pMatProj._11; vec.y = -(((2.0f * pos.y) / h) - 1.0f) / pMatProj._22; vec.z = 1.0f; // Create a view inverse matrix D3DXMatrixInverse(&m, NULL, &CDirectXRenderer::GetInstance()->Director()->View()); // Determine our ray's direction vRayDir.x = vec.x * m._11 + vec.y * m._21 + vec.z * m._31; vRayDir.y = vec.x * m._12 + vec.y * m._22 + vec.z * m._32; vRayDir.z = vec.x * m._13 + vec.y * m._23 + vec.z * m._33; // Determine our ray's origin vRayOrig.x = m._41; vRayOrig.y = m._42; vRayOrig.z = m._43; D3DXMatrixIdentity(&worldMat); //worldMat = aliveActors[0]->GetTrans(); D3DXMatrixInverse(&mInverse, NULL, &worldMat); D3DXVec3TransformCoord(&vROO, &vRayOrig, &mInverse); D3DXVec3TransformNormal(&vROD, &vRayDir, &mInverse); D3DXVec3Normalize(&vROD, &vROD); When using this code I'm able to detect a ray intersection via a sphere, but I have questions when determining an intersection via a plane. First off should I be using my vRayOrig & vRayDir variables for the plane intersection tests or should I be using the new vectors that are created for use in object space? When looking at a site like this for example: http://www.tar.hu/gamealgorithms/ch22lev1sec2.html I'm curious as to what D is in the equation AX + BY + CZ + D = 0 and how does it factor in to determining a plane intersection? Any help will be appreciated, thanks.

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• Parenting Opengl with Groups in LibGDX

  - by Rudy_TM

  I am trying to make an object child of a Group, but this object has a draw method that calls opengl to draw in the screen. Its class its this public class OpenGLSquare extends Actor { private static final ImmediateModeRenderer renderer = new ImmediateModeRenderer10(); private static Matrix4 matrix = null; private static Vector2 temp = new Vector2(); public static void setMatrix4(Matrix4 mat) { matrix = mat; } @Override public void draw(SpriteBatch batch, float arg1) { // TODO Auto-generated method stub renderer.begin(matrix, GL10.GL_TRIANGLES); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y0, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y0, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y0, 0f); renderer.end(); } } In my screen class I have this, i call it in the constructor MyGroupClass spriteLab = new MyGroupClass(spriteSheetLab); OpenGLSquare square = new OpenGLSquare(); square.setX0(100); square.setY0(200); square.setX1(400); square.setY1(280); square.color.set(Color.BLUE); square.setSize(); //spriteLab.addActorAt(0, clock); spriteLab.addActor(square); stage.addActor(spriteLab); And the render in the screen I have @Override public void render(float arg0) { this.gl.glClear(GL10.GL_COLOR_BUFFER_BIT |GL10.GL_DEPTH_BUFFER_BIT); stage.draw(); stage.act(Gdx.graphics.getDeltaTime()); } The problem its that when i use opengl with parent, it resets all the other chldren to position 0,0 and the opengl renderer paints the square in the exact position of the screen and not relative to the parent. I tried using batch.enableBlending() and batch.disableBlending() that fixes the position problem of the other children, but not the relative position of the opengl drawing and it also puts alpha to the glDrawing. What am i doing wrong?:/

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• Understanding how OpenGL blending works

  - by yuumei

  I am attempting to understand how OpenGL (ES) blending works. I am finding it difficult to understand the documentation and how the results of glBlendFunc and glBlendEquation effect the final pixel that is written. Do the source and destination out of glBlendFunc get added together with GL_FUNC_ADD by default? This seems wrong because "basic" blending of GL_ONE, GL_ONE would output 2,2,2,2 then (Source giving 1,1,1,1 and dest giving 1,1,1,1). I have written the following pseudo-code, what have I got wrong? struct colour { float r, g, b, a; }; colour blend_factor( GLenum factor, colour source, colour destination, colour blend_colour ) { colour colour_factor; float i = min( source.a, 1 - destination.a ); // From http://www.khronos.org/opengles/sdk/docs/man/xhtml/glBlendFunc.xml switch( factor ) { case GL_ZERO: colour_factor = { 0, 0, 0, 0 }; break; case GL_ONE: colour_factor = { 1, 1, 1, 1 }; break; case GL_SRC_COLOR: colour_factor = source; break; case GL_ONE_MINUS_SRC_COLOR: colour_factor = { 1 - source.r, 1 - source.g, 1 - source.b, 1 - source.a }; break; // ... } return colour_factor; } colour blend( colour & source, colour destination, GLenum source_factor, // from glBlendFunc GLenum destination_factor, // from glBlendFunc colour blend_colour, // from glBlendColor GLenum blend_equation // from glBlendEquation ) { colour source_colour = blend_factor( source_factor, source, destination, blend_colour ); colour destination_colour = blend_factor( destination_factor, source, destination, blend_colour ); colour output; // From http://www.khronos.org/opengles/sdk/docs/man/xhtml/glBlendEquation.xml switch( blend_equation ) { case GL_FUNC_ADD: output = add( source_colour, destination_colour ); case GL_FUNC_SUBTRACT: output = sub( source_colour, destination_colour ); case GL_FUNC_REVERSE_SUBTRACT: output = sub( destination_colour, source_colour ); } return output; } void do_pixel() { colour final_colour; // Blending if( enable_blending ) { final_colour = blend( current_colour_output, framebuffer[ pixel ], ... ); } else { final_colour = current_colour_output; } } Thanks!

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• Making a Camera look at a target Vector

  - by Peteyslatts

  I have a camera that works as long as its stationary. Now I'm trying to create a child class of that camera class that will look at its target. The new addition to the class is a method called SetTarget(). The method takes in a Vector3 target. The camera wont move but I need it to rotate to look at the target. If I just set the target, and then call CreateLookAt() (which takes in position, target, and up), when the object gets far enough away and underneath the camera, it suddenly flips right side up. So I need to transform the up vector, which currently always stays at Vector3.Up. I feel like this has something to do with taking the angle between the old direction vector and the new one (which I know can be expressed by target - position). I feel like this is all really vague, so here's the code for my base camera class: public class BasicCamera : Microsoft.Xna.Framework.GameComponent { public Matrix view { get; protected set; } public Matrix projection { get; protected set; } public Vector3 position { get; protected set; } public Vector3 direction { get; protected set; } public Vector3 up { get; protected set; } public Vector3 side { get { return Vector3.Cross(up, direction); } protected set { } } public BasicCamera(Game game, Vector3 position, Vector3 target, Vector3 up) : base(game) { this.position = position; this.direction = target - position; this.up = up; CreateLookAt(); projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.PiOver4, (float)Game.Window.ClientBounds.Width / (float)Game.Window.ClientBounds.Height, 1, 500); } public override void Update(GameTime gameTime) { // TODO: Add your update code here CreateLookAt(); base.Update(gameTime); } } And this is the code for the class that extends the above class to look at its target. class TargetedCamera : BasicCamera { public Vector3 target { get; protected set; } public TargetedCamera(Game game, Vector3 position, Vector3 target, Vector3 up) : base(game, position, target, up) { this.target = target; } public void SetTarget(Vector3 target) { direction = target - position; } protected override void CreateLookAt() { view = Matrix.CreateLookAt(position, target, up); } }

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• How do I access the preferences from my main dialog window? Also how do I add a new preference?

  - by Captain_Glen

  class PreferencesCalorieBurnerDialog(PreferencesDialog): __gtype_name__ = "PreferencesCalorieBurnerDialog" def finish_initializing(self, builder): # pylint: disable=E1002 """Set up the preferences dialog""" super(PreferencesCalorieBurnerDialog, self).finish_initializing(builder) # Bind each preference widget to gsettings settings = Gio.Settings("net.launchpad.calorie-burner") widget = self.builder.get_object('example_entry') settings.bind("example", widget, "text", Gio.SettingsBindFlags.DEFAULT) #Custom preference widget = self.builder.get_object('weight') settings.bind("weight", widget, "float", Gio.SettingsBindFlags.DEFAULT) Main Dialog self.PreferencesDialog.get_weight()???

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• Implementing a wheeled character controller

  - by Lazlo

  I'm trying to implement Boxycraft's character controller in XNA (with Farseer), as Bryan Dysmas did (minus the jumping part, yet). My current implementation seems to sometimes glitch in between two parallel planes, and fails to climb 45 degree slopes. (YouTube videos in links, plane glitch is subtle). How can I fix it? From the textual description, I seem to be doing it right. Here is my implementation (it seems like a huge wall of text, but it's easy to read. I wish I could simplify and isolate the problem more, but I can't): public Body TorsoBody { get; private set; } public PolygonShape TorsoShape { get; private set; } public Body LegsBody { get; private set; } public Shape LegsShape { get; private set; } public RevoluteJoint Hips { get; private set; } public FixedAngleJoint FixedAngleJoint { get; private set; } public AngleJoint AngleJoint { get; private set; } ... this.TorsoBody = BodyFactory.CreateRectangle(this.World, 1, 1.5f, 1); this.TorsoShape = new PolygonShape(1); this.TorsoShape.SetAsBox(0.5f, 0.75f); this.TorsoBody.CreateFixture(this.TorsoShape); this.TorsoBody.IsStatic = false; this.LegsBody = BodyFactory.CreateCircle(this.World, 0.5f, 1); this.LegsShape = new CircleShape(0.5f, 1); this.LegsBody.CreateFixture(this.LegsShape); this.LegsBody.Position -= 0.75f * Vector2.UnitY; this.LegsBody.IsStatic = false; this.Hips = JointFactory.CreateRevoluteJoint(this.TorsoBody, this.LegsBody, Vector2.Zero); this.Hips.MotorEnabled = true; this.AngleJoint = new AngleJoint(this.TorsoBody, this.LegsBody); this.FixedAngleJoint = new FixedAngleJoint(this.TorsoBody); this.Hips.MaxMotorTorque = float.PositiveInfinity; this.World.AddJoint(this.Hips); this.World.AddJoint(this.AngleJoint); this.World.AddJoint(this.FixedAngleJoint); ... public void Move(float m) // -1, 0, +1 { this.Hips.MotorSpeed = 0.5f * m; }

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• Displaylink USB show "Logo / Loading" on monitor

  - by Ken Le

  I tried with this problem for 2 years already. LOL, today, I install Ubuntu for I have to resolve it or I will back to stupid Windows 7. First, I have 3 monitors. My graphic card is support dual ( ATI Radeon ), so I have no problem on extend those multi monitor on VGA and DVI. The 3rd monitor is Displaylink USB. After installed everything required, when I reboot, the displaylink monitor show "Ubuntu ...." like logo / loading screen. I go to System Display , Detect monitor, it only show my 1st and 2nd, NO 3RD Displaylink. I can move my mouse between those 1st & 2nd, but the 3rd is only show the Ubuntu Screen. I press Ctrl+Alt+1, then screen switch to Displaylink USB 3RD monitor, but its "Terminal" not a desktop. Then I press Ctrl+Alt+7 , the screen switch back to my 1st, 2nd, and the displaylink 3rd is witch back to Logo / Ubuntu again. This is my /etc/X11/xorg.conf : Section "ServerLayout" Identifier "X.org Configured" Screen 0 "aticonfig-Screen[0]-0" 0 0 Screen 1 "DisplayLinkScreen" Leftof "aticonfig-Screen[0]-0" InputDevice "Mouse0" "CorePointer" InputDevice "Keyboard0" "CoreKeyboard" EndSection Section "Files" ModulePath "/usr/lib/xorg/modules" FontPath "/usr/share/fonts/X11/misc" FontPath "/usr/share/fonts/X11/cyrillic" FontPath "/usr/share/fonts/X11/100dpi/:unscaled" FontPath "/usr/share/fonts/X11/75dpi/:unscaled" FontPath "/usr/share/fonts/X11/Type1" FontPath "/usr/share/fonts/X11/100dpi" FontPath "/usr/share/fonts/X11/75dpi" FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType" FontPath "built-ins" EndSection Section "Module" Load "glx" Load "dri2" Load "dbe" Load "dri" Load "record" Load "extmod" EndSection Section "InputDevice" Identifier "Keyboard0" Driver "kbd" EndSection Section "InputDevice" Identifier "Mouse0" Driver "mouse" Option "Protocol" "auto" Option "Device" "/dev/input/mice" Option "ZAxisMapping" "4 5 6 7" EndSection Section "Monitor" Identifier "aticonfig-Monitor[0]-0" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" EndSection Section "Monitor" Identifier "DisplayLinkMonitor" EndSection Section "Monitor" Identifier "0-DFP1" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" Option "PreferredMode" "1680x1050" Option "TargetRefresh" "60" Option "Position" "0 0" Option "Rotate" "normal" Option "Disable" "false" EndSection Section "Monitor" Identifier "0-CRT2" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" Option "PreferredMode" "1920x1080" Option "TargetRefresh" "60" Option "Position" "1680 0" Option "Rotate" "normal" Option "Disable" "false" EndSection Section "Device" ### Available Driver options are:- ### Values: <i>: integer, <f>: float, <bool>: "True"/"False", ### <string>: "String", <freq>: "<f> Hz/kHz/MHz", ### <percent>: "<f>%" ### [arg]: arg optional #Option "NoAccel" # [<bool>] #Option "SWcursor" # [<bool>] #Option "Dac6Bit" # [<bool>] #Option "Dac8Bit" # [<bool>] #Option "BusType" # [<str>] #Option "CPPIOMode" # [<bool>] #Option "CPusecTimeout" # <i> #Option "AGPMode" # <i> #Option "AGPFastWrite" # [<bool>] #Option "AGPSize" # <i> #Option "GARTSize" # <i> #Option "RingSize" # <i> #Option "BufferSize" # <i> #Option "EnableDepthMoves" # [<bool>] #Option "EnablePageFlip" # [<bool>] #Option "NoBackBuffer" # [<bool>] #Option "DMAForXv" # [<bool>] #Option "FBTexPercent" # <i> #Option "DepthBits" # <i> #Option "PCIAPERSize" # <i> #Option "AccelDFS" # [<bool>] #Option "IgnoreEDID" # [<bool>] #Option "CustomEDID" # [<str>] #Option "DisplayPriority" # [<str>] #Option "PanelSize" # [<str>] #Option "ForceMinDotClock" # <freq> #Option "ColorTiling" # [<bool>] #Option "VideoKey" # <i> #Option "RageTheatreCrystal" # <i> #Option "RageTheatreTunerPort" # <i> #Option "RageTheatreCompositePort" # <i> #Option "RageTheatreSVideoPort" # <i> #Option "TunerType" # <i> #Option "RageTheatreMicrocPath" # <str> #Option "RageTheatreMicrocType" # <str> #Option "ScalerWidth" # <i> #Option "RenderAccel" # [<bool>] #Option "SubPixelOrder" # [<str>] #Option "ClockGating" # [<bool>] #Option "VGAAccess" # [<bool>] #Option "ReverseDDC" # [<bool>] #Option "LVDSProbePLL" # [<bool>] #Option "AccelMethod" # <str> #Option "DRI" # [<bool>] #Option "ConnectorTable" # <str> #Option "DefaultConnectorTable" # [<bool>] #Option "DefaultTMDSPLL" # [<bool>] #Option "TVDACLoadDetect" # [<bool>] #Option "ForceTVOut" # [<bool>] #Option "TVStandard" # <str> #Option "IgnoreLidStatus" # [<bool>] #Option "DefaultTVDACAdj" # [<bool>] #Option "Int10" # [<bool>] #Option "EXAVSync" # [<bool>] #Option "ATOMTVOut" # [<bool>] #Option "R4xxATOM" # [<bool>] #Option "ForceLowPowerMode" # [<bool>] #Option "DynamicPM" # [<bool>] #Option "NewPLL" # [<bool>] #Option "ZaphodHeads" # <str> Identifier "Card0" Driver "radeon" BusID "PCI:5:0:0" EndSection Section "Device" ### Available Driver options are:- ### Values: <i>: integer, <f>: float, <bool>: "True"/"False", ### <string>: "String", <freq>: "<f> Hz/kHz/MHz", ### <percent>: "<f>%" ### [arg]: arg optional #Option "ShadowFB" # [<bool>] #Option "Rotate" # <str> #Option "fbdev" # <str> #Option "debug" # [<bool>] Identifier "Card1" Driver "fbdev" BusID "PCI:5:0:0" EndSection Section "Device" ### Available Driver options are:- ### Values: <i>: integer, <f>: float, <bool>: "True"/"False", ### <string>: "String", <freq>: "<f> Hz/kHz/MHz", ### <percent>: "<f>%" ### [arg]: arg optional #Option "ShadowFB" # [<bool>] #Option "DefaultRefresh" # [<bool>] #Option "ModeSetClearScreen" # [<bool>] Identifier "Card2" Driver "vesa" BusID "PCI:5:0:0" EndSection Section "Device" Identifier "aticonfig-Device[0]-0" Driver "fglrx" Option "Monitor-DFP1" "0-DFP1" Option "Monitor-CRT2" "0-CRT2" BusID "PCI:5:0:0" EndSection Section "Device" Identifier "DisplayLinkDevice" Driver "displaylink" Option "fbdev" "/dev/fb1" Option "ShadowFB" "off" EndSection Section "Screen" Identifier "aticonfig-Screen[0]-0" Device "aticonfig-Device[0]-0" DefaultDepth 24 SubSection "Display" Viewport 0 0 Virtual 3600 1920 Depth 24 EndSubSection EndSection Section "Screen" Identifier "DisplayLinkScreen" Device "DisplayLinkDevice" Monitor "DisplayLinkMonitor" DefaultDepth 24 SubSection "Display" Depth 24 Modes "1920x1080" EndSubSection EndSection

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• 2D game - Missile shooting problem on Android

  - by Niksa

  Hello, I have to make a tank that sits still but moves his turret and shoots missiles. As this is my first Android application ever and I haven't done any game development either, I've come across a few problems... Now, I did the tank and the moving turret once I read the Android tutorial for the LunarLander sample code. So this code is based on the LunarLander code. But I'm having trouble doing the missile firing then SPACE button is being pressed. private void doDraw(Canvas canvas) { canvas.drawBitmap(backgroundImage, 0, 0, null); // draws the tank canvas.drawBitmap(tank, x_tank, y_tank, new Paint()); // draws and rotates the tank turret canvas.rotate((float) mHeading, (float) x_turret + mTurretWidth, y_turret); canvas.drawBitmap(turret, x_turret, y_turret, new Paint()); // draws the grenade that is a regular circle from ShapeDrawable class bullet.setBounds(x_bullet, y_bullet, x_bullet + width, y_bullet + height); bullet.draw(canvas); } UPDATE GAME method private void updateGame() throws InterruptedException { long now = System.currentTimeMillis(); if (mLastTime > now) return; double elapsed = (now - mLastTime) / 1000.0; mLastTime = now; // dUP and dDown, rotates the turret from 0 to 75 degrees. if (dUp) mHeading += 1 * (PHYS_SLEW_SEC * elapsed); if (mHeading >= 75) mHeading = 75; if (dDown) mHeading += (-1) * (PHYS_SLEW_SEC * elapsed); if (mHeading < 0) mHeading = 0; if (dSpace){ // missile Logic, a straight trajectorie for now x_bullet -= 1; y_bullet -= 1; //doesn't work, has to be updated every pixel or what? } boolean doKeyDown(int keyCode, KeyEvent msg) { boolean handled = false; synchronized (mSurfaceHolder) { if (keyCode == KeyEvent.KEYCODE_SPACE){ dSpace = true; handled = true; } if (keyCode == KeyEvent.KEYCODE_DPAD_UP){ dUp = true; handled = true; } if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN){ dDown = true; handled = true; } return handled; } } } a method run that runs the game... public void run() { while (mRun) { Canvas c = null; try { c = mSurfaceHolder.lockCanvas(null); synchronized (mSurfaceHolder) { if (mMode == STATE_RUNNING) updateGame(); doDraw(c); } } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { mSurfaceHolder.unlockCanvasAndPost(c); } } } } So the question would be, how do I make that the bullet is fired on a single SPACE key press from the turret to the end of the screen? Could you help me out here, I seem to be in the dark here... Thanks, Niksa

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• Why does creating dynamic bodies in JBox2D freeze my app?

  - by Amplify91

  My game hangs/freezes when I create dynamic bullet objects with Box2D and I don't know why. I am making a game where the main character can shoot bullets by the user tapping on the screen. Each touch event spawns a new FireProjectileEvent that is handled properly by an event queue. So I know my problem is not trying to create a new body while the box2d world is locked. My bullets are then created and managed by an object pool class like this: public Projectile getProjectile(){ for(int i=0;i<mProjectiles.size();i++){ if(!mProjectiles.get(i).isActive){ return mProjectiles.get(i); } } return mSpriteFactory.createProjectile(); } mSpriteFactory.createProjectile() leads to the physics component of the Projectile class creating its box2d body. I have narrowed the issue down to this method and it looks like this: public void create(World world, float x, float y, Vec2 vertices[], boolean dynamic){ BodyDef bodyDef = new BodyDef(); if(dynamic){ bodyDef.type = BodyType.DYNAMIC; }else{ bodyDef.type = BodyType.STATIC; } bodyDef.position.set(x, y); mBody = world.createBody(bodyDef); PolygonShape dynamicBox = new PolygonShape(); dynamicBox.set(vertices, vertices.length); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = dynamicBox; fixtureDef.density = 1.0f; fixtureDef.friction = 0.0f; mBody.createFixture(fixtureDef); mBody.setFixedRotation(true); } If the dynamic parameter is set to true my game freezes before crashing, but if it is false, it will create a projectile exactly how I want it just doesn't function properly (because a projectile is not a static object). Why does my program fail when I try to create a dynamic object at runtime but not when I create a static one? I have other dynamic objects (like my main character) that work fine. Any help would be greatly appreciated. This is a screenshot of a method profile I did: Especially notable is number 8. I'm just still unsure what I'm doing wrong. Other notes: I am using JBox2D 2.1.2.2. (Upgraded from 2.1.2.1 to try to fix this problem) When the application freezes, if I hit the back button, it appears to move my game backwards by one update tick. Very strange.

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• Rotate camera around player and set new forward directions

  - by Samurai Fox

  I have a 3rd person camera which can rotate around the player. When I look at the back of the player and press forward, player goes forward. Then I rotate 360 around the player and "forward direction" is tilted for 90 degrees. So every 360 turn there is 90 degrees of direction change. For example when camera is facing the right side of the player, when I press button to move forward, I want player to turn to the left and make that the "new forward". I have Player object with Camera as child object. Camera object has Camera script. Inside Camera script there are Player and Camera classes. Player object itself, has Input Controller. Also I'm making this script for joystick/ controller primarily. My camera script so far: using UnityEngine; using System.Collections; public class CameraScript : MonoBehaviour { public GameObject Target; public float RotateSpeed = 10, FollowDistance = 20, FollowHeight = 10; float RotateSpeedPerTime, DesiredRotationAngle, DesiredHeight, CurrentRotationAngle, CurrentHeight, Yaw, Pitch; Quaternion CurrentRotation; void LateUpdate() { RotateSpeedPerTime = RotateSpeed * Time.deltaTime; DesiredRotationAngle = Target.transform.eulerAngles.y; DesiredHeight = Target.transform.position.y + FollowHeight; CurrentRotationAngle = transform.eulerAngles.y; CurrentHeight = transform.position.y; CurrentRotationAngle = Mathf.LerpAngle(CurrentRotationAngle, DesiredRotationAngle, 0); CurrentHeight = Mathf.Lerp(CurrentHeight, DesiredHeight, 0); CurrentRotation = Quaternion.Euler(0, CurrentRotationAngle, 0); transform.position = Target.transform.position; transform.position -= CurrentRotation * Vector3.forward * FollowDistance; transform.position = new Vector3(transform.position.x, CurrentHeight, transform.position.z); Yaw = Input.GetAxis("Right Horizontal") * RotateSpeedPerTime; Pitch = Input.GetAxis("Right Vertical") * RotateSpeedPerTime; transform.Translate(new Vector3(Yaw, -Pitch, 0)); transform.position = new Vector3(transform.position.x, transform.position.y, transform.position.z); transform.LookAt(Target.transform); } }

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• Crash when using Cocos2d

  - by ipodfreak0313

  Sorry about the poor question title, it's just that this seems to big for a title. So here's the dirt: I am making a game (obviously) and I want the enemies to shoot (not necessarily at the player). I want the shoot method to be in the Enemies file, so as not to clutter up my HelloWorldLayer.m file even more. Here's what I'm using right now: HelloWorldLayer.m -(void)addEnemy:(BigAndStrongEnemy *)enemy { enemy = nil; if((arc4random() % 4) == 3) { enemy = [BigAndStrongEnemy enemy]; } else { enemy = [SmallAndFastEnemy enemy]; } if(buffDude.position.y > character.position.y || buffDude.position.y < (character.position.y + 10)) { } int rand = arc4random() % 320; if((arc4random() % 2 == 1)) { [enemy setPosition:ccp(0,rand)]; }else{ [enemy setPosition:ccp(480,rand)]; } [self animateEnemy:enemy]; [self addChild:enemy]; } -(void)animateEnemy:(BigAndStrongEnemy *)enemy2 { float randX = arc4random() % 480; float randY = arc4random() % 320; int rand = arc4random() % 320; CGPoint moveToPoint = CGPointMake(randX, (randY - rand)); [enemies addObject:enemy2]; action = [CCSequence actions: [CCMoveBy actionWithDuration:1 position:ccpMult(ccpNormalize(ccpSub(moveToPoint, enemy2.position)), 75)], [CCMoveBy actionWithDuration:3 position:ccp(buffDude.position.x,buffDude.position.y)], nil]; CCCallFuncO *a = [CCCallFuncO actionWithTarget:self selector:(@selector(shoot:)) object:enemy2]; CCSequence *s = [CCSequence actions:action,a, nil]; CCRepeatForever *repeat = [CCRepeatForever actionWithAction:s]; [enemy2 runAction:repeat]; } And here's the Shoot info from the Enemies class: Enemies.m: -(void)shoot:(id)sender { self = (BigAndStrongEnemy *)sender; [self shoot]; } -(void)spriteMoveFinished:(id)sender { CCSprite *b = (CCSprite *)sender; [self removeChild:b cleanup:YES]; } -(void)shoot { self = [CCSprite spriteWithFile:@"bigAndStrongEnemy.gif"]; CCSprite *b = [CCSprite spriteWithFile:@"bullet.gif"]; b.position = ccp(self.position.x,self.position.y); b.tag = 2; [self addChild:b]; [bullets addObject:b]; CGSize winSize = [[CCDirector sharedDirector] winSize]; CGPoint point = CGPointMake((winSize.width - (winSize.width - self.position.x)),0); [b runAction:[CCSequence actions: [CCMoveBy actionWithDuration:0.5 position:point], [CCCallFuncN actionWithTarget:self selector:@selector(spriteMoveFinished:)], nil]]; } Every time the 3 seconds goes by, the app crashes, and goes to the breakpoint in the CCCallFuncO file. I haven't touched it, is the thing. I am completely confused. Any help is greatly appreciated.

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• Using NumPy arrays as 2D mathematical vectors?

  - by CorundumGames

  Right now I'm using lists as position, velocity, and acceleration vectors in my game. Is that a better option than using NumPy's arrays (not the standard library's) as vectors (with float data types)? I'm frequently adding vectors and changing their values directly, then placing the values in these vectors into a Pygame Rect. The vector is used for position (because Rects can't hold floats, so we can't go "between" pixels), and the Rect is used for rendering (because Pygame will only take in Rects for rendering positions).

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• MarteEngine Tile Collision

  - by opiop65

  I need to add collision to my tile map using MarteEngine. MarteEngine is built of of slick2D. Here's my tile generation code: Code: public void render(GameContainer gc, StateBasedGame game, Graphics g) throws SlickException { for (int x = 0; x < 16; x++) { for (int y = 0; y < 16; y++) { map[x][y] = AIR; air.draw(x * GameWorld.tilesize, y * GameWorld.tilesize); } } for (int x = 0; x < 16; x++) { for (int y = 7; y < 8; y++) { map[x][y] = GRASS; grass.draw(x * tilesize, y * tilesize); } } for (int x = 0; x < 16; x++) { for (int y = 8; y < 10; y++) { map[x][y] = DIRT; dirt.draw(x * tilesize, y * tilesize); } } for (int x = 0; x < 16; x++) { for (int y = 10; y < 16; y++) { map[x][y] = STONE; stone.draw(x * tilesize, y * tilesize); } } super.render(gc, game, g); } And one of my tile classes (they're all the same, the image names are just different): Code: package MarteEngine; import org.newdawn.slick.Image; import org.newdawn.slick.SlickException; import it.randomtower.engine.entity.Entity; public class Grass extends Entity { public static Image grass = null; public Grass(float x, float y) throws SlickException { super(x, y); grass = new Image("res/grass.png"); setHitBox(0, 0, 50, 50); addType(SOLID); } } I tried to do it like this: Code: for (int x = 0; x < 16; x++) { for (int y = 7; y < 8; y++) { map[x][y] = GRASS; Grass.grass.draw(x * tilesize, y * tilesize); } } But it gave me a NullPointerException. No idea why, everything looks initialized right? I would be very grateful for some help!

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• OpenGL ES 2 jittery camera movement

  - by user16547

  First of all, I am aware that there's no camera in OpenGL (ES 2), but from my understanding proper manipulation of the projection matrix can simulate the concept of a camera. What I'm trying to do is make my camera follow my character. My game is 2D, btw. I think the principle is the following (take Super Mario Bros or Doodle Jump as reference - actually I'm trying to replicate the mechanics of the latter): when the caracter goes beyond the center of the screen (in the positive axis/direction), update the camera to be centred on the character. Else keep the camera still. I did accomplish that, however the camera movement is noticeably jittery and I ran out of ideas how to make it smoother. First of all, my game loop (following this article): private int TICKS_PER_SECOND = 30; private int SKIP_TICKS = 1000 / TICKS_PER_SECOND; private int MAX_FRAMESKIP = 5; @Override public void run() { loops = 0; if(firstLoop) { nextGameTick = SystemClock.elapsedRealtime(); firstLoop = false; } while(SystemClock.elapsedRealtime() > nextGameTick && loops < MAX_FRAMESKIP) { step(); nextGameTick += SKIP_TICKS; loops++; } interpolation = ( SystemClock.elapsedRealtime() + SKIP_TICKS - nextGameTick ) / (float)SKIP_TICKS; draw(); } And the following code deals with moving the camera. I was unsure whether to place it in step() or draw(), but it doesn't make a difference to my problem at the moment, as I tried both and neither seemed to fix it. center just represents the y coordinate of the centre of the screen at any time. Initially it is 0. The camera object is my own custom "camera" which basically is a class that just manipulates the view and projection matrices. if(character.getVerticalSpeed() >= 0) { //only update camera if going up float[] projectionMatrix = camera.getProjectionMatrix(); if( character.getY() > center) { center += character.getVerticalSpeed(); cameraBottom = center + camera.getBottom(); cameraTop = center + camera.getTop(); Matrix.orthoM(projectionMatrix, 0, camera.getLeft(), camera.getRight(), center + camera.getBottom(), center + camera.getTop(), camera.getNear(), camera.getFar()); } } Any thought about what I should try or what I am doing wrong? Update 1: I think I updated every value you can see on screen to check whether the jittery movement is affected by that, but nothing changed, so something must be fundamentally flawed with my approach/calculations.

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• rotating an object on an arc

  - by gardian06

  I am trying to get a turret to rotate on an arc, and have hit a wall. I have 8 possible starting orientations for the turrets, and want them to rotate on a 90 degree arc. I currently take the starting rotation of the turret, and then from that derive the positive, and negative boundary of the arc. because of engine restrictions (Unity) I have to do all of my tests against a value which is between [0,360], and due to numerical precision issues I can not test against specific values. I would like to write a general test without having to go in, and jury rig cases //my current test is: // member variables public float negBound; public float posBound; // found in Start() function (called immediately after construction) // eulerAngles.y is the the degree measure of the starting y rotation negBound = transform.eulerAngles.y-45; posBound = transform.eulerAngles.y+45; // insure that values are within bounds if(negBound<0){ negBound+=360; }else if(posBound>360){ posBound-=360; } // called from Update() when target not in firing line void Rotate(){ // controlls what direction if(transform.eulerAngles.y>posBound){ dir = -1; } else if(transform.eulerAngles.y < negBound){ dir = 1; } // rotate object } follows is a table of values for my different cases (please excuse my force formatting) read as base is the starting rotation of the turret, neg is the negative boundry, pos is the positive boundry, range is the acceptable range of values, and works is if it performs as expected with the current code. |base-|-neg-|-pos--|----------range-----------|-works-| |---0---|-315-|--45--|-315-0,0-45----------|----------| |--45--|---0---|--90--|-0-45,54-90----------|----x----| |-135-|---90--|-180-|-90-135,135-180---|----x----| |-180-|--135-|-225-|-135-180,180-225-|----x----| |-225-|--180-|-270-|-180-225,225-270-|----x----| |-270-|--225-|-315-|-225-270,270-315-|----------| |-315-|--270-|---0---|--270-315,315-0---|----------| I will need to do all tests from derived, or stored values, but can not figure out how to get all of my cases to work simultaneously. //I attempted to concatenate the 2 tests: if((transform.eulerAngles.y>posBound)&&(transform.eulerAngles.y < negBound)){ dir *= -1; } this caused only the first case to be successful // I attempted to store a opposite value, and do a void Rotate(){ // controlls what direction if((transform.eulerAngles.y > posBound)&&(transform.eulerAngles.y<oposite)){ dir = -1; } else if((transform.eulerAngles.y < negBound)&&(transform.eulerAngles.y>oposite)){ dir = 1; } // rotate object } this causes the opposite situation as indicated on the table. What am I missing here?

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• Accounting for waves when doing planar reflections

  - by CloseReflector

  I've been studying Nvidia's examples from the SDK, in particular the Island11 project and I've found something curious about a piece of HLSL code which corrects the reflections up and down depending on the state of the wave's height. Naturally, after examining the brief paragraph of code: // calculating correction that shifts reflection up/down according to water wave Y position float4 projected_waveheight = mul(float4(input.positionWS.x,input.positionWS.y,input.positionWS.z,1),g_ModelViewProjectionMatrix); float waveheight_correction=-0.5*projected_waveheight.y/projected_waveheight.w; projected_waveheight = mul(float4(input.positionWS.x,-0.8,input.positionWS.z,1),g_ModelViewProjectionMatrix); waveheight_correction+=0.5*projected_waveheight.y/projected_waveheight.w; reflection_disturbance.y=max(-0.15,waveheight_correction+reflection_disturbance.y); My first guess was that it compensates for the planar reflection when it is subjected to vertical perturbation (the waves), shifting the reflected geometry to a point where is nothing and the water is just rendered as if there is nothing there or just the sky: Now, that's the sky reflecting where we should see the terrain's green/grey/yellowish reflection lerped with the water's baseline. My problem is now that I cannot really pinpoint what is the logic behind it. Projecting the actual world space position of a point of the wave/water geometry and then multiplying by -.5f, only to take another projection of the same point, this time with its y coordinate changed to -0.8 (why -0.8?). Clues in the code seem to indicate it was derived with trial and error because there is redundancy. For example, the author takes the negative half of the projected y coordinate (after the w divide): float waveheight_correction=-0.5*projected_waveheight.y/projected_waveheight.w; And then does the same for the second point (only positive, to get a difference of some sort, I presume) and combines them: waveheight_correction+=0.5*projected_waveheight.y/projected_waveheight.w; By removing the divide by 2, I see no difference in quality improvement (if someone cares to correct me, please do). The crux of it seems to be the difference in the projected y, why is that? This redundancy and the seemingly arbitrary selection of -.8f and -0.15f lead me to conclude that this might be a combination of heuristics/guess work. Is there a logical underpinning to this or is it just a desperate hack? Here is an exaggeration of the initial problem which the code fragment fixes, observe on the lowest tessellation level. Hopefully, it might spark an idea I'm missing. The -.8f might be a reference height from which to deduce how much to disturb the texture coordinate sampling the planarly reflected geometry render and -.15f might be the lower bound, a security measure.

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• C# OpenGL problem with animation

  - by user3696303

  there is a program that simulates a small satellite and requires that a rotation animation of the satellite along the three axes. But when you try to write an animation problem during compilation: the program simply closes (shutdown occurs when swapbuffers, mainloop, redisplay), when you write the easiest programs have the same problem arose. Trying to catch exception by try-catch but here is not exception. How to solve this? I suffer with this a few days. Work in c# visual studio 2008 framework namespace WindowsFormsApplication6 { public partial class Form1 : Form { public Form1() { try { InitializeComponent(); AnT1.InitializeContexts(); } catch(Exception) { Glut.glutDisplayFunc(Draw); Glut.glutTimerFunc(50, Timer, 0); Glut.glutMainLoop(); } } void Timer(int Unused) { Glut.glutPostRedisplay(); Glut.glutTimerFunc(50, Timer, 0); } private void AnT1_Load(object sender, EventArgs e) { Glut.glutInit(); Glut.glutInitDisplayMode(Glut.GLUT_RGB | Glut.GLUT_DOUBLE | Glut.GLUT_DEPTH); Gl.glClearColor(255, 255, 255, 1); Gl.glViewport(0, 0, AnT1.Width, AnT1.Height); Gl.glMatrixMode(Gl.GL_PROJECTION); Gl.glLoadIdentity(); Glu.gluPerspective(45, (float)AnT1.Width / (float)AnT1.Height, 0.1, 200); Gl.glMatrixMode(Gl.GL_MODELVIEW); Gl.glLoadIdentity(); Gl.glEnable(Gl.GL_DEPTH_TEST); Gl.glClear(Gl.GL_COLOR_BUFFER_BIT | Gl.GL_DEPTH_BUFFER_BIT); Gl.glPushMatrix(); double xy = 0.2; Gl.glTranslated(xy, 0, 0); xy += 0.2; Draw(); Glut.glutSwapBuffers(); Glut.glutPostRedisplay(); Gl.glPushMatrix(); Draw(); Gl.glPopMatrix(); } void Draw() { Gl.glLoadIdentity(); Gl.glColor3f(0.502f, 0.502f, 0.502f); Gl.glTranslated(-1, 0, -6); Gl.glRotated(95, 1, 0, 0); Glut.glutSolidCylinder(0.7, 2, 60, 60); Gl.glLoadIdentity(); Gl.glColor3f(0, 0, 0); Gl.glTranslated(-1, 0, -6); Gl.glRotated(95, 1, 0, 0); Glut.glutWireCylinder(0.7, 2, 20, 20); } } }

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• How to fix footer cutting off content in an above div [closed]

  - by sqyttles

  I am working on this web page: https://ws.missouristate.edu/factbook/execsummary/ and as you can see the page footer is covering the content. I have tried to adjust many CSS properties such as overflow, position, height, float, etc. in firebug and none of my edits have had any positive effect. I am even using a clearing div. Perhaps I am overlooking something pretty easy. How do I prevent the footer from covering up the table content?

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• Iscroll Wrapper doesnt get a height

  - by MCSell

  I got the following code: <div data-role="content" height="100%" data-iscroll> <div class="homebutton_zeile"> <a id="picture_home" href="#pictrues"> <div class="homebutton_all"> <div class="homebutton_name">Picture</div> <div class="homebutton_picture"> <img src="images/picture.png" alt="image" style="position: relative;"> </div> </div> </a> </div> </div> </div> My Classes of CSS .homebutton_zeile{ width: 100%; height: 30%; } .homebutton_all{ width: 30%; height: 90%; float:left; margin-left: 2%; margin-top:15px; } .homebutton_picture{ position: relative; width: 100%; height: 85%; float: left; background-color: #AAC7BD; border: 1px solid black; border-radius: 15px; box-shadow:8px 8px 8px #666; } .homebutton_name{ text-align:center; position: relative; top:-10px; width: 100%; height: 15%; margin-left: auto; text-decoration:none; color:black; } I am Using: iscroll.js jquery 1.8.2 jquery mobile 1.2.0 jqery mobile iscrollview. And if its needed to know jstorage.js and fastclick.js But the div above is not getting a height at the wrapper of iscroll. There is also a login before and this page will be shown automatically after the login after a $.mobile.changePage("#home"); function. I tried to do it as first page before the function of changePage and it gave me the same effect. If i put a   for example after the <div data-role="content" height="100%" data-iscroll>&nbps; The Wrapper get a height of 15px for the &nbps; but not for the images inside.

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