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  • Keypress Left is called twice in Update when key is pressed only once

    - by Simran kaur
    I have a piece of code that is changing the position of player when left key is pressed. It is inside of Update() function. I know, Update is called multiple times, but since I have an ifstatement to check if left arrow is pressed, it should update only once. I have tested using print statement that once pressed, it gets called twice. Problem: Position updated twice when key is pressed only once. Below given is the structure of my code: void Update() { if (Input.GetKeyDown (KeyCode.LeftArrow)) { print ("PRESSEEEEEEEEEEEEEEEEEEDDDDDDDDDDDDDD"); } } I looked up on web and what was suggested id this: if (Event.current.type == EventType.KeyDown && Event.current.keyCode == KeyCode.LeftArrow) { print("pressed"); } But, It gives me an error that says: Object reference not set to instance of an object How can I fix this?

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  • A* how make natural look path?

    - by user11177
    I've been reading this: http://theory.stanford.edu/~amitp/GameProgramming/Heuristics.html But there are some things I don't understand, for example the article says to use something like this for pathfinding with diagonal movement: function heuristic(node) = dx = abs(node.x - goal.x) dy = abs(node.y - goal.y) return D * max(dx, dy) I don't know how do set D to get a natural looking path like in the article, I set D to the lowest cost between adjacent squares like it said, and I don't know what they meant by the stuff about the heuristic should be 4*D, that does not seem to change any thing. This is my heuristic function and move function: def heuristic(self, node, goal): D = 10 dx = abs(node.x - goal.x) dy = abs(node.y - goal.y) return D * max(dx, dy) def move_cost(self, current, node): cross = abs(current.x - node.x) == 1 and abs(current.y - node.y) == 1 return 19 if cross else 10 Result: The smooth sailing path we want to happen: The rest of my code: http://pastebin.com/TL2cEkeX

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  • Best practices in managing character states

    - by TheBroodian
    While in development of a character, I feel like I'm digging myself deeper into a hole every time I add more functionality to him, creating more bugs and it seems like my code is tripping over itself all over the place. What are the best practices when managing character states for a character that has a large selection of abilities and actions that they can perform, without their abilities interrupting each other and creating a mess overall?

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  • What is the simplest way to render video into memory (for drawing to a texture) in .NET?

    - by sebf
    In my project I would like to be able to play back video on surfaces in the world. I intend to do this by having the video frames rendered to a block of memory, then use this to update a texture each frame. Everything is in place - except for the part that actually gets the video. I have looked on Google and found that the video library world is very expansive (and geared towards video processing), and am having trouble finding a suitable one. FFMpeg is very comprehensive, but is an entire suite and would take a good amount of work to integrate. So far the most promising library I've found is the one based on the VLC player libraries - by virtue of it using the same resources as VLC Player it is known to be very capable; it also renders to blocks of memory, but the API (at least of the one on Codeplex) is more of a port of the C++ API rather than a managed wrapper. The 'solution' can be any wrapper/API/library, but with characteristics that make it suitable for use in a rendering engine, namely: Renders the video frame data to memory, so it can be picked up and passed to a texture on the GPU easily. Super simple - all that is needed is a way to load, jump and render a frame programatically - ideally it would use the systems codecs and not require an assortment of plugins. Permissive license (LGPL or more free-er) .NET bindings at least; all the better if it is natively managed Can anyone suggest a lightweight, (.NET) library, that can take a video file, and spit out some frames into a byte[]?

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  • Unity: Assigning String value in inspector

    - by Marc Pilgaard
    I got an issue with Unity I can't seem to comprehend, and it is possibly very simple: I am trying to write a simple piece of code in JavaScript where a button toggles the activation of a shield, by dragging a prefab with Resources.load("ActivateShieldPreFab") and destroying it again (Haven't implemented that yet). I wish to assign this button through the inspector, so I have created a string variable which appears as intended in the inspector. Though it doesn't seem to register the inspector input, even though I changed the value through the inspector. It only provides the error: "Input Key named: is unknown" When the button name is assigned within the code, there is no issues. Code as follows: var ShieldOn = false; var stringbutton : String; function Start(){ } function Update () { if(Input.GetKey(stringbutton) && ShieldOn != true) { Instantiate(Resources.load("ActivateShieldPreFab"), Vector3 (0, 0, 0), Quaternion.identity); ShieldOn = true; } } Hope somebody can help, in advance... Thanks

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  • OpenGL directional light creating black spots

    - by AnonymousDeveloper
    I probably ought to start by saying that I suspect the problem is that one of my vectors is not in the correct "space", but I don't know for sure. I am having a strange problem with a directional light. When I move the camera away from (0.0, 0.0, 0.0) it creates tiny black spots that grow larger as the distance increases. I apologize ahead of time for the length of the code. Vertex shader: #version 410 core in vec3 vf_normal; in vec3 vf_bitangent; in vec3 vf_tangent; in vec2 vf_textureCoordinates; in vec3 vf_vertex; out vec3 tc_normal; out vec3 tc_bitangent; out vec3 tc_tangent; out vec2 tc_textureCoordinates; out vec3 tc_vertex; uniform mat3 vf_m_normal; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform float vf_te_inner; uniform float vf_te_outer; void main() { tc_normal = vf_normal; tc_bitangent = vf_bitangent; tc_tangent = vf_tangent; tc_textureCoordinates = vf_textureCoordinates; tc_vertex = vf_vertex; gl_Position = vf_m_mvp * vec4(vf_vertex, 1.0); } Tessellation Control shader: #version 410 core layout (vertices = 3) out; in vec3 tc_normal[]; in vec3 tc_bitangent[]; in vec3 tc_tangent[]; in vec2 tc_textureCoordinates[]; in vec3 tc_vertex[]; out vec3 te_normal[]; out vec3 te_bitangent[]; out vec3 te_tangent[]; out vec2 te_textureCoordinates[]; out vec3 te_vertex[]; uniform float vf_te_inner; uniform float vf_te_outer; uniform vec4 vf_l_color; uniform vec3 vf_l_position; uniform mat4 vf_m_depthBias; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform sampler2D vf_t_diffuse; uniform sampler2D vf_t_normal; uniform sampler2DShadow vf_t_shadow; uniform sampler2D vf_t_specular; #define ID gl_InvocationID float getTessLevelInner(float distance0, float distance1) { float avgDistance = (distance0 + distance1) / 2.0; return clamp((vf_te_inner - avgDistance), 1.0, vf_te_inner); } float getTessLevelOuter(float distance0, float distance1) { float avgDistance = (distance0 + distance1) / 2.0; return clamp((vf_te_outer - avgDistance), 1.0, vf_te_outer); } void main() { te_normal[gl_InvocationID] = tc_normal[gl_InvocationID]; te_bitangent[gl_InvocationID] = tc_bitangent[gl_InvocationID]; te_tangent[gl_InvocationID] = tc_tangent[gl_InvocationID]; te_textureCoordinates[gl_InvocationID] = tc_textureCoordinates[gl_InvocationID]; te_vertex[gl_InvocationID] = tc_vertex[gl_InvocationID]; float eyeToVertexDistance0 = distance(vec3(0.0), vec4(vf_m_view * vec4(tc_vertex[0], 1.0)).xyz); float eyeToVertexDistance1 = distance(vec3(0.0), vec4(vf_m_view * vec4(tc_vertex[1], 1.0)).xyz); float eyeToVertexDistance2 = distance(vec3(0.0), vec4(vf_m_view * vec4(tc_vertex[2], 1.0)).xyz); gl_TessLevelOuter[0] = getTessLevelOuter(eyeToVertexDistance1, eyeToVertexDistance2); gl_TessLevelOuter[1] = getTessLevelOuter(eyeToVertexDistance2, eyeToVertexDistance0); gl_TessLevelOuter[2] = getTessLevelOuter(eyeToVertexDistance0, eyeToVertexDistance1); gl_TessLevelInner[0] = getTessLevelInner(eyeToVertexDistance2, eyeToVertexDistance0); } Tessellation Evaluation shader: #version 410 core layout (triangles, equal_spacing, cw) in; in vec3 te_normal[]; in vec3 te_bitangent[]; in vec3 te_tangent[]; in vec2 te_textureCoordinates[]; in vec3 te_vertex[]; out vec3 g_normal; out vec3 g_bitangent; out vec4 g_patchDistance; out vec3 g_tangent; out vec2 g_textureCoordinates; out vec3 g_vertex; uniform float vf_te_inner; uniform float vf_te_outer; uniform vec4 vf_l_color; uniform vec3 vf_l_position; uniform mat4 vf_m_depthBias; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat3 vf_m_normal; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform sampler2D vf_t_diffuse; uniform sampler2D vf_t_displace; uniform sampler2D vf_t_normal; uniform sampler2DShadow vf_t_shadow; uniform sampler2D vf_t_specular; vec2 interpolate2D(vec2 v0, vec2 v1, vec2 v2) { return vec2(gl_TessCoord.x) * v0 + vec2(gl_TessCoord.y) * v1 + vec2(gl_TessCoord.z) * v2; } vec3 interpolate3D(vec3 v0, vec3 v1, vec3 v2) { return vec3(gl_TessCoord.x) * v0 + vec3(gl_TessCoord.y) * v1 + vec3(gl_TessCoord.z) * v2; } float amplify(float d, float scale, float offset) { d = scale * d + offset; d = clamp(d, 0, 1); d = 1 - exp2(-2*d*d); return d; } float getDisplacement(vec2 t0, vec2 t1, vec2 t2) { float displacement = 0.0; vec2 textureCoordinates = interpolate2D(t0, t1, t2); vec2 vector = ((t0 + t1 + t2) / 3.0); float sampleDistance = sqrt((vector.x * vector.x) + (vector.y * vector.y)); sampleDistance /= ((vf_te_inner + vf_te_outer) / 2.0); displacement += texture(vf_t_displace, textureCoordinates).x; displacement += texture(vf_t_displace, textureCoordinates + vec2(-sampleDistance, -sampleDistance)).x; displacement += texture(vf_t_displace, textureCoordinates + vec2(-sampleDistance, sampleDistance)).x; displacement += texture(vf_t_displace, textureCoordinates + vec2( sampleDistance, sampleDistance)).x; displacement += texture(vf_t_displace, textureCoordinates + vec2( sampleDistance, -sampleDistance)).x; return (displacement / 5.0); } void main() { g_normal = normalize(interpolate3D(te_normal[0], te_normal[1], te_normal[2])); g_bitangent = normalize(interpolate3D(te_bitangent[0], te_bitangent[1], te_bitangent[2])); g_patchDistance = vec4(gl_TessCoord, (1.0 - gl_TessCoord.y)); g_tangent = normalize(interpolate3D(te_tangent[0], te_tangent[1], te_tangent[2])); g_textureCoordinates = interpolate2D(te_textureCoordinates[0], te_textureCoordinates[1], te_textureCoordinates[2]); g_vertex = interpolate3D(te_vertex[0], te_vertex[1], te_vertex[2]); float displacement = getDisplacement(te_textureCoordinates[0], te_textureCoordinates[1], te_textureCoordinates[2]); float d2 = min(min(min(g_patchDistance.x, g_patchDistance.y), g_patchDistance.z), g_patchDistance.w); d2 = amplify(d2, 50, -0.5); g_vertex += g_normal * displacement * 0.1 * d2; gl_Position = vf_m_mvp * vec4(g_vertex, 1.0); } Geometry shader: #version 410 core layout (triangles) in; layout (triangle_strip, max_vertices = 3) out; in vec3 g_normal[3]; in vec3 g_bitangent[3]; in vec4 g_patchDistance[3]; in vec3 g_tangent[3]; in vec2 g_textureCoordinates[3]; in vec3 g_vertex[3]; out vec3 f_tangent; out vec3 f_bitangent; out vec3 f_eyeDirection; out vec3 f_lightDirection; out vec3 f_normal; out vec4 f_patchDistance; out vec4 f_shadowCoordinates; out vec2 f_textureCoordinates; out vec3 f_vertex; uniform vec4 vf_l_color; uniform vec3 vf_l_position; uniform mat4 vf_m_depthBias; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat3 vf_m_normal; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform sampler2D vf_t_diffuse; uniform sampler2D vf_t_normal; uniform sampler2DShadow vf_t_shadow; uniform sampler2D vf_t_specular; void main() { int index = 0; while (index < 3) { vec3 vertexNormal_cameraspace = vf_m_normal * normalize(g_normal[index]); vec3 vertexTangent_cameraspace = vf_m_normal * normalize(f_tangent); vec3 vertexBitangent_cameraspace = vf_m_normal * normalize(f_bitangent); mat3 TBN = transpose(mat3( vertexTangent_cameraspace, vertexBitangent_cameraspace, vertexNormal_cameraspace )); vec3 eyeDirection = -(vf_m_view * vf_m_model * vec4(g_vertex[index], 1.0)).xyz; vec3 lightDirection = normalize(-(vf_m_view * vec4(vf_l_position, 1.0)).xyz); f_eyeDirection = TBN * eyeDirection; f_lightDirection = TBN * lightDirection; f_normal = normalize(g_normal[index]); f_patchDistance = g_patchDistance[index]; f_shadowCoordinates = vf_m_depthBias * vec4(g_vertex[index], 1.0); f_textureCoordinates = g_textureCoordinates[index]; f_vertex = (vf_m_model * vec4(g_vertex[index], 1.0)).xyz; gl_Position = gl_in[index].gl_Position; EmitVertex(); index ++; } EndPrimitive(); } Fragment shader: #version 410 core in vec3 f_bitangent; in vec3 f_eyeDirection; in vec3 f_lightDirection; in vec3 f_normal; in vec4 f_patchDistance; in vec4 f_shadowCoordinates; in vec3 f_tangent; in vec2 f_textureCoordinates; in vec3 f_vertex; out vec4 fragColor; uniform vec4 vf_l_color; uniform vec3 vf_l_position; uniform mat4 vf_m_depthBias; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform sampler2D vf_t_diffuse; uniform sampler2D vf_t_normal; uniform sampler2DShadow vf_t_shadow; uniform sampler2D vf_t_specular; vec2 poissonDisk[16] = vec2[]( vec2(-0.94201624, -0.39906216), vec2( 0.94558609, -0.76890725), vec2(-0.09418410, -0.92938870), vec2( 0.34495938, 0.29387760), vec2(-0.91588581, 0.45771432), vec2(-0.81544232, -0.87912464), vec2(-0.38277543, 0.27676845), vec2( 0.97484398, 0.75648379), vec2( 0.44323325, -0.97511554), vec2( 0.53742981, -0.47373420), vec2(-0.26496911, -0.41893023), vec2( 0.79197514, 0.19090188), vec2(-0.24188840, 0.99706507), vec2(-0.81409955, 0.91437590), vec2( 0.19984126, 0.78641367), vec2( 0.14383161, -0.14100790) ); float random(vec3 seed, int i) { vec4 seed4 = vec4(seed,i); float dot_product = dot(seed4, vec4(12.9898, 78.233, 45.164, 94.673)); return fract(sin(dot_product) * 43758.5453); } float amplify(float d, float scale, float offset) { d = scale * d + offset; d = clamp(d, 0, 1); d = 1 - exp2(-2.0 * d * d); return d; } void main() { vec3 lightColor = vf_l_color.xyz; float lightPower = vf_l_color.w; vec3 materialDiffuseColor = texture(vf_t_diffuse, f_textureCoordinates).xyz; vec3 materialAmbientColor = vec3(0.1, 0.1, 0.1) * materialDiffuseColor; vec3 materialSpecularColor = texture(vf_t_specular, f_textureCoordinates).xyz; vec3 n = normalize(texture(vf_t_normal, f_textureCoordinates).rgb * 2.0 - 1.0); vec3 l = normalize(f_lightDirection); float cosTheta = clamp(dot(n, l), 0.0, 1.0); vec3 E = normalize(f_eyeDirection); vec3 R = reflect(-l, n); float cosAlpha = clamp(dot(E, R), 0.0, 1.0); float visibility = 1.0; float bias = 0.005 * tan(acos(cosTheta)); bias = clamp(bias, 0.0, 0.01); for (int i = 0; i < 4; i ++) { float shading = (0.5 / 4.0); int index = i; visibility -= shading * (1.0 - texture(vf_t_shadow, vec3(f_shadowCoordinates.xy + poissonDisk[index] / 3000.0, (f_shadowCoordinates.z - bias) / f_shadowCoordinates.w))); }\n" fragColor.xyz = materialAmbientColor + visibility * materialDiffuseColor * lightColor * lightPower * cosTheta + visibility * materialSpecularColor * lightColor * lightPower * pow(cosAlpha, 5); fragColor.w = texture(vf_t_diffuse, f_textureCoordinates).w; } The following images should be enough to give you an idea of the problem. Before moving the camera: Moving the camera just a little. Moving it to the center of the scene.

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  • HLSL: An array of textures and sampler states

    - by nate142
    The shader must switch between multiple textures depending on the Alpha value of the original texture for each pixel. Now this would word fine if I didn't have to worry about SamplerStates. I have created my array of textures and can select a texture based on the Alpha value of the pixel. But how do I create an Array of SamplerStates and link it to my array of textures? I attempted to treat the SamplerState as a function by adding the (int i) but that didn't work. Also I can't use Texture.Sample since this is shader model 2.0. //shader model 2.0 (DX9) texture subTextures[255]; SamplerState MeshTextureSampler(int i) { Texture = (subTextures[i]); }; float4 SampleCompoundTexture(float2 texCoord, float4 diffuse) { float4 SelectedColor = SAMPLE_TEXTURE(Texture, texCoord); int i = SelectedColor.a; texture SelectedTx = subTextures[i]; return tex2D(MeshTextureSampler(i), texCoord) * diffuse; }

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  • Coordinate and positioning problem on iOS with cocos2d-x

    - by Vexille
    I'm using cocos2d-x alongside with Marmalade and running some tests and tutorials before starting an actual project with them. So far things are working reasonably well on the windows simulator, Android and even on Blackberry's Playbook, but on iOS devices (iPhone and iPad) the positioning seems to be off. To make things clearer, I put together a scene that just draws an image in the middle of the screen. It worked as expected on everything else, but this is the result I got on an iPhone: To get the coordinates for the center of the screen I'm using the VisibleRect class from the TestCpp sample. It just uses sharedOpenGLView to get the visible size and visible origin, and calculate the center from that. CCSprite* test = CCSprite::create("Ball.png", CCRectMake(0, 0, 80, 80) ); test->setPosition( ccp(VisibleRect::center().x, VisibleRect::center().y) ); this->addChild(test); Also I have a noBorder policy set on AppDelegate: CCEGLView::sharedOpenGLView()->setDesignResolutionSize(designSize.width, designSize.height, kResolutionNoBorder); One funny thing is that I tried to deploy the TestCpp sample project to some iOS devices and it worked reasonably well on the iPhone, but on the iPad the application was only being drawn on a small portion of the screen - just like what happened on the iPhone when I tried using the ShowAll policy.

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  • Selection of a mesh with arbitrary region

    - by Tigran
    Considering example: I have a mesh(es) on the OpenGL screen and would like to select a part of it (say for delete purpose). There is a clear way to do the selction via Ray Tracing, or via Selection provided by OpenGL itself. But, for my users, considering that meshes can get wired surfaces, I need to implement a selection via a Arbitrary closed region, so all triangles that appears present inside that region has to be selected. To be more clear, here is screen shot: I want all triangles inside black polygon to be selected, identified, whatever in some way. How can I achieve that ?

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  • 2d ball collision code problem XNA, over accelerated balls and stick together sometimes. help please? [closed]

    - by Sivan
    public static void Collision(Ball ball1, Ball ball2) { Vector3 x = new Vector3((ball1.BallPosition.X - ball2.BallPosition.X), (ball1.BallPosition.Y - ball2.BallPosition.Y), 0); x.Normalize(); Vector3 v1 = new Vector3(ball1.Speed, 0); float x1 = Vector3.Dot(x, v1); Vector3 v1x = x * x1; Vector3 v1y = v1 - v1x; x = -x; Vector3 v2 = new Vector3(ball2.Speed, 0); float x2 = Vector3.Dot(x, v2); Vector3 v2x = x * x2; Vector3 v2y = v2 - v2x; float m1 = 12, m2 = 4; float combinedMass = m1 + m2; Vector3 newVelA = (v1x * ((m1 - m2) / combinedMass)) + (v2x * ((2f * m2) / combinedMass)) + v1y; Vector3 newVelB = (v1x * ((2f * m1) / combinedMass)) + (v2x * ((m2 - m1) / combinedMass)) + v2y; ball1.Speed = new Vector2(newVelA.X, newVelA.Y); ball2.Speed = new Vector2(newVelB.X,newVelB.Y ); }

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  • Understanding dot notation

    - by Starkers
    Here's my interpretation of dot notation: a = [2,6] b = [1,4] c = [0,8] a . b . c = (2*6)+(1*4)+(0*8) = 12 + 4 + 0 = 16 What is the significance of 16? Apparently it's a scalar. Am I right in thinking that a scalar is the number we times a unit vector by to get a vector that has a scaled up magnitude but the same direction as the unit vector? So again, what is the relevance of 16? When is it used? It's not the magnitude of all the vectors added up. The magnitude of all of them is calculated as follows: sqrt( ax * ax + ay * ay ) + sqrt( bx * bx + by * by ) + sqrt( cx * cx + cy * cy) sqrt( 2 * 2 + 6 * 6 ) + sqrt( 1 * 1 + 4 * 4 ) + sqrt( 0 * 0 + 8 * 8) sqrt( 4 + 36 ) + sqrt( 1 + 16 ) + sqrt( 0 + 64) sqrt( 40 ) + sqrt( 17 ) + sqrt( 64) 6.3 + 4.1 + 8 10.4 + 8 18.4 So I don't really get this diagram: Attempting with sensible numbers: a = [1,0] b = [4,3] a . b = (1*0) + (4*3) = 0 + 12 = 12 So what exactly is a . b describing here? The magnitude of that vector? Because that isn't right: the 'a.b' vector = [4,0] sqrt( x*x + y*y ) sqrt( 4*4 + 0*0 ) sqrt( 16 + 0 ) 4 So what is 12 describing?

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  • Correcting Lighting in Stencil Reflections

    - by Reanimation
    I'm just playing around with OpenGL seeing how different methods of making shadows and reflections work. I've been following this tutorial which describes using GLUT_STENCIL's and MASK's to create a reasonable interpretation of a reflection. Following that and a bit of tweaking to get things to work, I've come up with the code below. Unfortunately, the lighting isn't correct when the reflection is created. glPushMatrix(); plane(); //draw plane that reflection appears on glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); glDepthMask(GL_FALSE); glEnable(GL_STENCIL_TEST); glStencilFunc(GL_ALWAYS, 1, 0xFFFFFFFF); glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE); plane(); //draw plane that acts as clipping area for reflection glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); glDepthMask(GL_TRUE); glStencilFunc(GL_EQUAL, 1, 0xFFFFFFFF); glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP); glDisable(GL_DEPTH_TEST); glPushMatrix(); glScalef(1.0f, -1.0f, 1.0f); glTranslatef(0,2,0); glRotatef(180,0,1,0); sphere(radius, spherePos); //draw object that you want to have a reflection glPopMatrix(); glEnable(GL_DEPTH_TEST); glDisable(GL_STENCIL_TEST); sphere(radius, spherePos); //draw object that creates reflection glPopMatrix(); It looked really cool to start with, then I noticed that the light in the reflection isn't correct. I'm not sure that it's even a simple fix because effectively the reflection is also a sphere but I thought I'd ask here none-the-less. I've tried various rotations (seen above the first time the sphere is drawn) but it doesn't seem to work. I figure it needs to rotate around the Y and Z axis but that's not correct. Have I implemented the rotation wrong or is there a way to correct the lighting?

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  • how to keep display tick rate steady when using continuous collision detection?

    - by nas Ns
    (I've just found about this forum). I hope it is ok to repost my question again here. I posted this question at stackoverflow, but it looks like I might get better help here. Here is the question: I've implemented basic particles motion simulation with continuous collision detection. But there is small issue in display. Assume simple case of circles moving inside square. All elastic collisions. no firction. All motion is constant speed. No forces are involved, no gravity. So when a particle is moving, it is always moving at constant speed (in between collisions) What I do now is this: Let the simulation time step be 1 second (for example). This is the time step simulation is advanced before displaying the new state (unless there is a collision sooner than this). At start of each time step, time for the next collision between any particles or a particle with a wall is determined. Call this the TOC time; let’s say TOC was .5 seconds in this case. Since TOC is smaller than the standard time step, then the system is moved by TOC and the new system is displayed so that the new display shows any collisions as just taking place (say 2 circles just touched each other’s, or a circle just touched a wall) Next, the collision(s) are resolved (i.e. speeds updated, changed directions etc..). A new step is started. The same thing happens. Now assume there is no collision detected within the next 1 second (those 2 circles above will not be in collision any more, even though they are still touching, due to their speeds showing they are moving apart now), Hence, simulation time is advanced now by the full one second, the standard time step, and particles are moved on the screen using 1 second simulation time and new display is shown. You see what has just happened: One frame ran for .5 seconds, but the next frame runs for 1 second, may be the 3rd frame is displayed after 2 seconds, may be the 4th frame is displayed after 2.8 seconds (because TOC was .8 seconds then) and so on. What happens is that the motion of a particle on the screen appears to speed up or slow down, even though it is moving at constant speed and was not even involved in a collision. i.e. Looking at one particle on its own, I see it suddenly speeding up or slowing down, becuase another particle had hit a wall. This is because the display tick is not uniform. i.e. the frame rate update is changing, giving the false illusion that a particle is moving at non-constant speed while in fact it is moving at constant speed. The motion on the screen is not smooth, since the screen is not updating at constant rate. I am not able to figure how to fix this. If I want to show 2 particles at the moment of the collision, I must draw the screen at different times. Drawing the screen always at the same tick interval, results in seeing 2 particles before the collision, and then after the collision, and not just when they colliding, which looked bad when I tried it. So, how do real games handle this issue? How to display things in order to show collisions when it happen, yet keep the display tick constant? These 2 requirements seem to contradict each other’s.

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  • How do I get the point coords of a rotated SFML shaperect?

    - by user15498
    I am trying to get collisions of bullets working, and am using SFML. I am using code to get the position of the points of the rectangle for collisions, however I think there's a way to do this without having to get points but by simply getting the points from SFML, since the shape is a rectangle and the points are stored in that way. Is there a way to do that? Through a combination of getPoint() and getGlobalBounds() maybe? While on this topic, is it better to use shapeRects or sprites? I used to only use sprites, however with the addition of textures and more low level stuff I think it would be best to switch to using rectangles and setting their size.

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  • Which code module should map physical keys to abstract keys?

    - by Paul Manta
    How do you bridge the gap between the library's low-level event system and your engine's high-level event system? (I'm not necessarily talking about key events, but also about quit events.) At the top level of my event system, I send out KeyPressedEvents, KeyRelesedEvents and others of this kind. These high-level events only contain the abstract values of the keys (they don't say that Space way pressed, but that the JumpKey was pressed, for example). Whose responsibility should it be to map the "JumpKey" to an actual key on the keyboard?

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  • Marching squares: Finding multiple contours within one source field?

    - by TravisG
    Principally, this is a follow-up-question to a problem from a few weeks ago, even though this is about the algorithm in general without application to my actual problem. The algorithm basically searches through all lines in the picture, starting from the top left of it, until it finds a pixel that is a border. In pseudo-C++: int start = 0; for(int i=0; i<amount_of_pixels; ++i) { if(pixels[i] == border) { start = i; break; } } When it finds one, it starts the marching squares algorithm and finds the contour to whatever object the pixel belongs to. Let's say I have something like this: Where everything except the color white is a border. And have found the contour points of the first blob: For the general algorithm it's over. It found a contour and has done its job. How can I move on to the other two blobs to find their contours as well?

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  • Very basic OpenGL ES 2 error

    - by user16547
    This is an incredibly simple shader, yet I'm having a lot of trouble understanding what's wrong with it. I'm trying to send a float to my fragment shader. Its purpose is to adjust the alpha of the fragment colour. Here is my fragment shader: precision mediump float; uniform sampler2D u_Texture; uniform float u_Alpha; varying vec2 v_TexCoordinate; void main() { gl_FragColor = texture2D(u_Texture, v_TexCoordinate); gl_FragColor.a *= u_Alpha; } and below is my rendering method. I get a 1282 (invalid operation) on the GLES20.glUniform1f(u_Alpha, alpha); line. alpha is 1 (but I tried other values as well) and transparent is true: public void render() { GLES20.glUseProgram(mProgram); if(transparent) { GLES20.glEnable(GLES20.GL_BLEND); GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA); GLES20.glUniform1f(u_Alpha, alpha); } Matrix.setIdentityM(mModelMatrix, 0); Matrix.rotateM(mModelMatrix, 0, angle, 0, 0, 1); Matrix.translateM(mModelMatrix, 0, x, y, z); Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0); Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0); GLES20.glUniformMatrix4fv(u_MVPMatrix, 1, false, mMVPMatrix, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbo[0]); GLES20.glVertexAttribPointer(a_Position, 3, GLES20.GL_FLOAT, false, 12, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbo[1]); GLES20.glVertexAttribPointer(a_TexCoordinate, 2, GLES20.GL_FLOAT, false, 8, 0); //snowTexture start GLES20.glActiveTexture(GLES20.GL_TEXTURE0); GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]); GLES20.glUniform1i(u_Texture, 0); GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, ibo[0]); GLES20.glDrawElements(GLES20.GL_TRIANGLE_STRIP, indices.capacity(), GLES20.GL_UNSIGNED_BYTE, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0); GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, 0); if(transparent) { GLES20.glDisable(GLES20.GL_BLEND); } GLES20.glUseProgram(0); }

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  • Can i change the order of these OpenGL / Win32 calls?

    - by Adam Naylor
    I've been adapting the NeHe ogl/win32 code to be more object orientated and I don't like the way some of the calls are structured. The example has the following pseudo structure: Register window class Change display settings with a DEVMODE Adjust window rect Create window Get DC Find closest matching pixel format Set the pixel format to closest match Create rendering context Make that context current Show the window Set it to foreground Set it to having focus Resize the GL scene Init GL The points in bold are what I want to move into a rendering class (the rest are what I see being pure win32 calls) but I'm not sure if I can call them after the win32 calls. Essentially what I'm aiming for is to encapsulate the Win32 calls into a Platform::Initiate() type method and the rest into a sort of Renderer::Initiate() method. So my question essentially boils down to: "Would OpenGL allow these methods to be called in this order?" Register window class Adjust window rect Create window Get DC Show the window Set it to foreground Set it to having focus Change display settings with a DEVMODE Find closest matching pixel format Set the pixel format to closest match Create rendering context Make that context current Resize the GL scene Init GL (obviously passing through the appropriate window handles and device contexts.) Thanks in advance.

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  • How can be data oriented programming applied for GUI system?

    - by Miro
    I've just learned basics of Data oriented programming design, but I'm not very familiar with that yet. I've also read Pitfalls of Object Oriented Programming GCAP 09. It seems that data oriented programming is much better idea for games, than OOP. I'm just creating my own GUI system and it's completely OOP. I'm thinking if is data oriented programming design applicable for structured things like GUI. The main problem I see is that every type widget has different data, so I can hardly group them into arrays. Also every type of widget renders differently so I still need to call virtual functions.

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  • How to make natural-looking paths with A* on a grid?

    - by user11177
    I've been reading this: http://theory.stanford.edu/~amitp/GameProgramming/Heuristics.html But there are some things I don't understand, for example the article says to use something like this for pathfinding with diagonal movement: function heuristic(node) = dx = abs(node.x - goal.x) dy = abs(node.y - goal.y) return D * max(dx, dy) I don't know how do set D to get a natural looking path like in the article, I set D to the lowest cost between adjacent squares like it said, and I don't know what they meant by the stuff about the heuristic should be 4*D, that does not seem to change any thing. This is my heuristic function and move function: def heuristic(self, node, goal): D = 10 dx = abs(node.x - goal.x) dy = abs(node.y - goal.y) return D * max(dx, dy) def move_cost(self, current, node): cross = abs(current.x - node.x) == 1 and abs(current.y - node.y) == 1 return 19 if cross else 10 Result: The smooth sailing path we want to happen: The rest of my code: http://pastebin.com/TL2cEkeX

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  • Indexed Drawing in OpenGL not working

    - by user2050846
    I am trying to render 2 types of primitives- - points ( a Point Cloud ) - triangles ( a Mesh ) I am rendering points simply without any index arrays and they are getting rendered fine. To render the meshes I am using indexed drawing with the face list array having the indices of the vertices to be rendered as Triangles. Vertices and their corresponding vertex colors are stored in their corresponding buffers. But the indexed drawing command do not draw anything. The code is as follows- Main Display Function: void display() { simple->enable(); simple->bindUniform("MV",modelview); simple->bindUniform("P", projection); // rendering Point Cloud glBindVertexArray(vao); // Vertex buffer Point Cloud glBindBuffer(GL_ARRAY_BUFFER,vertexbuffer); glEnableVertexAttribArray(0); glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,0); // Color Buffer point Cloud glBindBuffer(GL_ARRAY_BUFFER,colorbuffer); glEnableVertexAttribArray(1); glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE,0,0); // Render Colored Point Cloud //glDrawArrays(GL_POINTS,0,model->vertexCount); glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); // ---------------- END---------------------// //// Floor Rendering glBindBuffer(GL_ARRAY_BUFFER,fl); glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,0); glVertexAttribPointer(1,4,GL_FLOAT,GL_FALSE,0,(void *)48); glDrawArrays(GL_QUADS,0,4); glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); // -----------------END---------------------// //Rendering the Meshes //////////// PART OF CODE THAT IS NOT DRAWING ANYTHING //////////////////// glBindVertexArray(vid); for(int i=0;i<NUM_MESHES;i++) { glBindBuffer(GL_ARRAY_BUFFER,mVertex[i]); glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,0); glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE,0,(void *)(meshes[i]->vertexCount*sizeof(glm::vec3))); //glDrawArrays(GL_TRIANGLES,0,meshes[i]->vertexCount); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,mFace[i]); //cout<<gluErrorString(glGetError()); glDrawElements(GL_TRIANGLES,meshes[i]->faceCount*3,GL_FLOAT,(void *)0); glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); } glUseProgram(0); glutSwapBuffers(); glutPostRedisplay(); } Point Cloud Buffer Allocation Initialization: void initGLPointCloud() { glGenBuffers(1,&vertexbuffer); glGenBuffers(1,&colorbuffer); glGenBuffers(1,&fl); //Populates the position buffer glBindBuffer(GL_ARRAY_BUFFER,vertexbuffer); glBufferData(GL_ARRAY_BUFFER, model->vertexCount * sizeof (glm::vec3), &model->positions[0], GL_STATIC_DRAW); //Populates the color buffer glBindBuffer(GL_ARRAY_BUFFER, colorbuffer); glBufferData(GL_ARRAY_BUFFER, model->vertexCount * sizeof (glm::vec3), &model->colors[0], GL_STATIC_DRAW); model->FreeMemory(); // To free the not needed memory, as the data has been already // copied on graphic card, and wont be used again. glBindBuffer(GL_ARRAY_BUFFER,0); } Meshes Buffer Initialization: void initGLMeshes(int i) { glBindBuffer(GL_ARRAY_BUFFER,mVertex[i]); glBufferData(GL_ARRAY_BUFFER,meshes[i]->vertexCount*sizeof(glm::vec3)*2,NULL,GL_STATIC_DRAW); glBufferSubData(GL_ARRAY_BUFFER,0,meshes[i]->vertexCount*sizeof(glm::vec3),&meshes[i]->positions[0]); glBufferSubData(GL_ARRAY_BUFFER,meshes[i]->vertexCount*sizeof(glm::vec3),meshes[i]->vertexCount*sizeof(glm::vec3),&meshes[i]->colors[0]); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,mFace[i]); glBufferData(GL_ELEMENT_ARRAY_BUFFER,meshes[i]->faceCount*sizeof(glm::vec3), &meshes[i]->faces[0],GL_STATIC_DRAW); meshes[i]->FreeMemory(); //glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,0); } Initialize the Rendering, load and create shader and calls the mesh and PCD initializers. void initRender() { simple= new GLSLShader("shaders/simple.vert","shaders/simple.frag"); //Point Cloud //Sets up VAO glGenVertexArrays(1, &vao); glBindVertexArray(vao); initGLPointCloud(); //floorData glBindBuffer(GL_ARRAY_BUFFER, fl); glBufferData(GL_ARRAY_BUFFER, sizeof(floorData), &floorData[0], GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER,0); glBindVertexArray(0); //Meshes for(int i=0;i<NUM_MESHES;i++) { if(i==0) // SET up the new vertex array state for indexed Drawing { glGenVertexArrays(1, &vid); glBindVertexArray(vid); glGenBuffers(NUM_MESHES,mVertex); glGenBuffers(NUM_MESHES,mColor); glGenBuffers(NUM_MESHES,mFace); } initGLMeshes(i); } glEnable(GL_DEPTH_TEST); } Any help would be much appreciated, I have been breaking my head on this problem since 3 days, and still it is unsolved.

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  • XNA Drag Gestures - fractional delta values

    - by Den
    I have an issue with objects moving roughly twice as far as expected when dragging them. I am comparing my application to the standard TouchGestureSample sample from MSDN. For some reason in my application gesture samples have fractional positions and deltas. Both are using same Microsoft.Xna.Framework.Input.Touch.dll, v4.0.30319. I am running both apps using standard Windows Phone Emulator. I am setting my break point immediately after this line of code in a simple Update method: GestureSample gesture = TouchPanel.ReadGesture(); Typical values in my app: Delta = {X:-13.56522 Y:4.166667} Position = {X:184.6956 Y:417.7083} Typical values in sample app: Delta = {X:7 Y:16} Position = {X:497 Y:244} Have anyone seen this issue? Does anyone have any suggestions? Thank you.

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  • Whole map design vs. tiles array design

    - by Mikalichov
    I am working on a 2D RPG, which will feature the usual dungeon/town maps (pre-generated). I am using tiles, that I will then combine to make the maps. My original plan was to assemble the tiles using Photoshop, or some other graphic program, in order to have one bigger picture that I could then use as a map. However, I have read on several places people talking about how they used arrays to build their map in the engine (so you give an array of x tiles to your engine, and it assemble them as a map). I can understand how it's done, but it seems a lot more complicated to implement, and I can't see obvious avantages. What is the most common method, and what are advantages/disadvantages of each?

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  • Learning C++ but wanting to develop iOS Apps

    - by DiscreteGenius
    I'm a computer engineering student and taking my second programming class. I'm learning C++ using "C++ Primer Plus" 5th edition by Prata. I want to develop for iOS. I understand the main language for Xcode is Objective-C. Am I hurting myself by learning C++ before any other language (notably before my desired lang Objective-C)? There's got to be a reason the university requires C++ to learn as a basis language. Please offer any helpful guidance or how I should go about this. Thanks//

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  • How to pass one float as four unsigned chars to shader by glVertexPointAttrib?

    - by Kog
    For each vertex I use two floats as position and four unsigned bytes as color. I want to store all of them in one table, so I tried casting those four unsigned bytes to one float, but I am unable to do that correctly... All in all, my tests came to one point: GLfloat vertices[] = { 1.0f, 0.5f, 0, 1.0f, 0, 0 }; glEnableVertexAttribArray(0); glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), vertices); // VER1 - draws red triangle // unsigned char colors[] = { 0xff, 0, 0, 0xff, 0xff, 0, 0, 0xff, 0xff, 0, 0, // 0xff }; // glEnableVertexAttribArray(1); // glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), // colors); // VER2 - draws greenish triangle (not "pure" green) // float f = 255 << 24 | 255; //Hex:0xff0000ff // float colors2[] = { f, f, f }; // glEnableVertexAttribArray(1); // glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), // colors2); // VER3 - draws red triangle int i = 255 << 24 | 255; //Hex:0xff0000ff int colors3[] = { i, i, i }; glEnableVertexAttribArray(1); glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), colors3); glDrawArrays(GL_TRIANGLES, 0, 3); Above code is used to draw one simple red triangle. My question is - why do versions 1 and 3 work correctly, while version 2 draws some greenish triangle? Hex values are one I read by marking variable during debug. They are equal for version 2 and 3 - so what causes the difference?

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