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• How can I find a position between 4 vertices in a fragment shader?

  - by c4sh

  I'm creating a shader with SharpDX (DirectX11 in C#) that takes a segment (2 points) from the output of a Vertex Shader and then passes them to a Geometry Shader, which converts this line into a rectangle (4 points) and assigns the four corners a texture coordinate. After that I want a Fragment Shader (which recieves the interpolated position and the interpolated texture coordinates) that checks the depth at the "spine of the rectangle" (that is, in the line that passes through the middle of the rectangle. The problem is I don't know how to extract the position of the corresponding fragment at the spine of the rectangle. This happens because I have the texture coordinates interpolated, but I don't know how to use them to get the fragment I want, because the coordinate system of a) the texture and b) the position of my fragment in screen space are not the same. Thanks a lot for any help.

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• Manually writing a dx11 tessellation shader

  - by Tudor

  I am looking for resources on what are the steps of manually implementing tessellation (I'm using Unity cg). Today it seems that it is all the rage to hide most of the gpu code far away and use rather rigid simplifications such as unity's SURFace shaders. And it seems useless unless you're doing supeficial stuff. A little background: I have procedurally generated meshes (using marching cubes) which have quality normals but no UVs and no Tangents. I have successfully written a custom vertex and fragment shader to do triplanar texture and bumpmap projection as well as some custom stuff (custom lighting, procedurally warping the texture for variation etc). I am using the GPU Gems book as reference. Now I need to implement tessellation, but It seems I must calculate the tangents at runtime by swizzling normals (ctrl+f this in gems: <normal.z, normal.y, -normal.x>) before the tessellator gets them. And I also need to keep my custom vert+frag setup (with my custom parameters/textures being passed between them) - so apparently I cannot use surface shaders. Can anyone provide some guidence?

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• Geometry shader for multiple primitives

  - by Byte56

  How can I create a geometry shader that can handle multiple primitives? For example when creating a geometry shader for triangles, I define a layout like so: layout(triangles) in; layout(triangle_strip, max_vertices=3) out; But if I use this shader then lines or points won't show up. So adding: layout(triangles) in; layout(triangle_strip, max_vertices=3) out; layout(lines) in; layout(line_strip, max_vertices=2) out; The shader will compile and run, but will only render lines (or whatever the last primitive defined is). So how do I define a single geometry shader that will handle multiple types of primitives? Or is that not possible and I need to create multiple shader programs and change shader programs before drawing each type?

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• Compute bounding quad of a sphere with vertex shader

  - by Ben Jones

  I'm trying to implement an algorithm from a graphics paper and part of the algorithm is rendering spheres of known radius to a buffer. They say that they render the spheres by computing the location and size in a vertex shader and then doing appropriate shading in a fragment shader. Any guesses as to how they actually did this? The position and radius are known in world coordinates and the projection is perspective. Does that mean that the sphere will be projected as a circle? Thanks!

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• How can I run the pixel shader effect?

  - by Yashwinder

  Stated below is the code for my pixel shader which I am rendering after the vertex shader. I have set the wordViewProjection matrix in my program but I don't know to set the progress variable i.e in my pixel shader file which will make the image displayed by the help of a quad to give out transition effect. Here is the code for my pixel shader program::: As my pixel shader is giving a static effect and now I want to use it to give some effect. So for this I have to add a progress variable in my pixel shader and initialize to the Constant table function i.e constantTable.SetValue(D3DDevice,"progress",progress ); I am having the problem in using this function for progress in my program. Anybody know how to set this variable in my program. And my new pixel shader code is float progress : register(C0); sampler2D implicitInput : register(s0); sampler2D oldInput : register(s1); struct VS_OUTPUT { float4 Position : POSITION; float4 Color : COLOR0; float2 UV : TEXCOORD 0; }; float4 Blinds(float2 uv) { if(frac(uv.y * 5) < progress) { return tex2D(implicitInput, uv); } else { return tex2D(oldInput, uv); } } // Pixel Shader { return Blinds(input.UV); }

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• shader coding: calculate screen coordinates of fragment

  - by Jay

  Good morning, I'm new to shader coding and trying to implement some visual effects code in shaders using billboards. (Yes, I couldn't have picked anything harder to start with, but I'm lucky that way) Setup: I have rendered the full screen z depth to an array of floats in a previous pass. In the fragment shader I need the scene depth where the rendered fragment is displayed (to see if it's occluded). I can use tex2d() to get the depth value if I have the screen coordinates of the point being rendered in the fragment shader. Question: In the fragment shader how do you calculate the screen coordinates of the pixel (in the range 0-1.0)? Is the position passed to the fragment shader a pixel offset? If so, I guess it would be: float2( position.x / screen-width, position.y / screen-height ) Thanks for any help/

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• Which Graphics/Geometry abstraction to choose?

  - by Robz

  I've been thinking about the design for a browser app on the HTML5 canvas that simulates a 2D robot zooming around, sensing the world around it. I decided to do this from scratch just for fun. I need shapes, like polygons, circles, and lines in order to model the robot and the world it lives in. These shapes need to be drawn with different appearance attributes, like border/fill style/width/color. I also need to have geometry functions to detect intersections and containment for the robot's sensors and so that the robot doesn't go inside stuff. One idea for functions is to have two totally separate libraries, one to implement graphics (like drawShape(context, shape)) and one for geometry operations (like shapeIntersectsShape(shape1, shape2)). Or, in a more object-oriented approach, the shape objects themselves could implement methods to do their own graphics (shape.draw(context)) and geometry operations (shape1.intersects(shape2)). Then there is the data itself: whether the data to draw a shape and the data to do geometric operations on that shape should be encapsulated within the same object, or be separate structures (where one would contain the other, or both be contained inside another structure). How do existing applications that do graphics/geometry stuff deal with this? Is there one model that is best, or is each good for certain applications? Should the fact that I'm using Javascript instead of a more classical language change how I approach the design?

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• Would like some help in understanding rendering geometry vs textures

  - by Anon

  So I was just pondering whether it is more taxing on the GPU to render geometry or a texture. What I'm trying to see is whether there is a huge difference in rendering two scenes with the same setup: Scene 1: Example Object: A dirt road (nothing else) Geometry: Detailed road, with all the bumps, cracks and so forth done in the mesh Scene 2: Example Object: A dirt road (nothing else) Geometry: A simple mesh, in a form of a road, but in this case maps and textures are simulating cracks, bumps, etc... So of these two, which one is likely to tax the hardware more? Or is it not a like for like comparison? What would be the best way of doing something like this? Go heavy on the textures? Or have a blend of both?

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• GLSL check if fragment is on geometry

  - by mokaschitta

  I am currently writing the positions of my geometry to the RGB channels of gl_FragColor and I would like to write 1.0 to the alpha channel if the fragment is part of geometry, and 0.0 if its empty. Is there a simple way to tell if a fragment is geometry or not? Maybe through gl_FragCoord.z? thanks

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• Generating geometry when using VBO

  - by onedayitwillmake

  Currently I am working on a project in which I generate geometry based on the players movement. A glorified very long trail, composed of quads. I am doing this by storing a STD::Vector, and removing the oldest verticies once enough exist, and then calling glDrawArrays. I am interested in switching to a shader based model, usually examples I see the VBO is generated at start and then that's basically it. What is the best route to go about creating geometry in real time, using shader / VBO approach

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• iOS - pass UIImage to shader as texture

  - by martin pilch

  I am trying to pass UIImage to GLSL shader. The fragment shader is: varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform sampler2D inputImageTexture2; void main() { highp vec4 color = texture2D(inputImageTexture, textureCoordinate); highp vec4 color2 = texture2D(inputImageTexture2, textureCoordinate); gl_FragColor = color * color2; } What I want to do is send images from camera and do multiply blend with texture. When I just send data from camera, everything is fine. So problem should be with sending another texture to shader. I am doing it this way: - (void)setTexture:(UIImage*)image forUniform:(NSString*)uniform { CGSize sizeOfImage = [image size]; CGFloat scaleOfImage = [image scale]; CGSize pixelSizeOfImage = CGSizeMake(scaleOfImage * sizeOfImage.width, scaleOfImage * sizeOfImage.height); //create context GLubyte * spriteData = (GLubyte *)malloc(pixelSizeOfImage.width * pixelSizeOfImage.height * 4 * sizeof(GLubyte)); CGContextRef spriteContext = CGBitmapContextCreate(spriteData, pixelSizeOfImage.width, pixelSizeOfImage.height, 8, pixelSizeOfImage.width * 4, CGImageGetColorSpace(image.CGImage), kCGImageAlphaPremultipliedLast); //draw image into context CGContextDrawImage(spriteContext, CGRectMake(0.0, 0.0, pixelSizeOfImage.width, pixelSizeOfImage.height), image.CGImage); //get uniform of texture GLuint uniformIndex = glGetUniformLocation(__programPointer, [uniform UTF8String]); //generate texture GLuint textureIndex; glGenTextures(1, &textureIndex); glBindTexture(GL_TEXTURE_2D, textureIndex); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); //create texture glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, pixelSizeOfImage.width, pixelSizeOfImage.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, textureIndex); //"send" to shader glUniform1i(uniformIndex, 1); free(spriteData); CGContextRelease(spriteContext); } Uniform for texture is fine, glGetUniformLocation function do not returns -1. The texture is PNG file of resolution 2000x2000 pixels. PROBLEM: When the texture is passed to shader, I have got "black screen". Maybe problem are parameters of the CGContext or parameters of the function glTexImage2D Thank you

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• Geometry Shader: distortions

  - by Christophe Lionet

  This is a cross-question from Stack Overflow, I thought it would be more appropriate here. There is a lot of code I could be posting. To avoid overloading the page with code, I will post any part of the code if requested. I am working from the ParticleGS DirectX10 sample, to build a geometry shader based particle system in DirectX 11. Using the sample code, and changing it to my liking, I am able to draw a single quad (which is essentially one particle constantly recreating itself). However, I noticed a problem which was similar to one I once had: the rendered shape is distorted. Here is a video showcasing what is happening. http://youtu.be/6NY_hxjMfwY Now, I used to have this issue when using several effects together, when I realised that I needed to explicitely set the geometry shader to null for the other effects. I solved this problem, as you can see in the video, as the rest of the scene is drawing properly. Note that some sides are being culled somehow, although I turned off culling in my main render state. The texturing is fine too, the texture draws with appropriate proportions relative to the quad. I really don't see what I could be doing wrong here... what would cause the geometry shader to behave in such a way? Again, I will post any piece code you will request.

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• Weird y offset when using custom frag shader (Cocos2d-x)

  - by Mister Guacamole

  I'm trying to mask a sprite so I wrote a simple fragment shader that renders only the pixels that are not hidden under another texture (the mask). The problem is that it seems my texture has its y-coordinate offset after passing through the shader. This is the init method of the sprite (GroundZone) I want to mask: bool GroundZone::initWithSize(Size size) { // [...] // Setup the mask of the sprite m_mask = RenderTexture::create(textureWidth, textureHeight); m_mask->retain(); m_mask->setKeepMatrix(true); Texture2D *maskTexture = m_mask->getSprite()->getTexture(); maskTexture->setAliasTexParameters(); // Disable linear interpolation on the mask // Load the custom frag shader with a default vert shader as the sprite’s program FileUtils *fileUtils = FileUtils::getInstance(); string vertexSource = ccPositionTextureA8Color_vert; string fragmentSource = fileUtils->getStringFromFile( fileUtils->fullPathForFilename("CustomShader_AlphaMask_frag.fsh")); GLProgram *shader = new GLProgram; shader->initWithByteArrays(vertexSource.c_str(), fragmentSource.c_str()); shader->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_POSITION, GLProgram::VERTEX_ATTRIB_POSITION); shader->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD, GLProgram::VERTEX_ATTRIB_TEX_COORDS); shader->link(); CHECK_GL_ERROR_DEBUG(); shader->updateUniforms(); CHECK_GL_ERROR_DEBUG(); int maskTexUniformLoc = shader->getUniformLocationForName("u_alphaMaskTexture"); shader->setUniformLocationWith1i(maskTexUniformLoc, 1); this->setShaderProgram(shader); shader->release(); // [...] } These are the custom drawing methods for actually drawing the mask over the sprite: You need to know that m_mask is modified externally by another class, the onDraw() method only render it. void GroundZone::draw(Renderer *renderer, const kmMat4 &transform, bool transformUpdated) { m_renderCommand.init(_globalZOrder); m_renderCommand.func = CC_CALLBACK_0(GroundZone::onDraw, this, transform, transformUpdated); renderer->addCommand(&m_renderCommand); Sprite::draw(renderer, transform, transformUpdated); } void GroundZone::onDraw(const kmMat4 &transform, bool transformUpdated) { GLProgram *shader = this->getShaderProgram(); shader->use(); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, m_mask->getSprite()->getTexture()->getName()); glActiveTexture(GL_TEXTURE0); } Below is the method (located in another class, GroundLayer) that modify the mask by drawing a line from point start to point end. Both points are in Cocos2d coordinates (Point (0,0) is down-left). void GroundLayer::drawTunnel(Point start, Point end) { // To dig a line, we need first to get the texture of the zone we will be digging into. Then we get the // relative position of the start and end point in the zone's node space. Finally we use the custom shader to // draw a mask over the existing texture. for (auto it = _children.begin(); it != _children.end(); it++) { GroundZone *zone = static_cast<GroundZone *>(*it); Point nodeStart = zone->convertToNodeSpace(start); Point nodeEnd = zone->convertToNodeSpace(end); // Now that we have our two points converted to node space, it's easy to draw a mask that contains a line // going from the start point to the end point and that is then applied over the current texture. Size groundZoneSize = zone->getContentSize(); RenderTexture *rt = zone->getMask(); rt->begin(); { // Draw a line going from start and going to end in the texture, the line will act as a mask over the // existing texture DrawNode *line = DrawNode::create(); line->retain(); line->drawSegment(nodeStart, nodeEnd, 20, Color4F::RED); line->visit(); } rt->end(); } } Finally, here's the custom shader I wrote. #ifdef GL_ES precision mediump float; #endif varying vec2 v_texCoord; uniform sampler2D u_texture; uniform sampler2D u_alphaMaskTexture; void main() { float maskAlpha = texture2D(u_alphaMaskTexture, v_texCoord).a; float texAlpha = texture2D(u_texture, v_texCoord).a; float blendAlpha = (1.0 - maskAlpha) * texAlpha; // Show only where mask is invisible vec3 texColor = texture2D(u_texture, v_texCoord).rgb; gl_FragColor = vec4(texColor, blendAlpha); return; } I got a problem with the y coordinates. Indeed, it seems that once it has passed through my custom shader, the sprite's texture is not at the right place: Without custom shader (the sprite is the brown thing): With custom shader: What's going on here? Thanks :) EDIT It looks like after passing through the shader when I set the position of the sprite I set it in points, with (0,0) being in the top-right. Indeed, when I do sprite->setPosition(320, 480), the sprite is perfectly placed at the top of the screen.

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• Queries regarding Geometry Shaders

  - by maverick9888

  I am dealing with geometry shaders using GL_ARB_geometry_shader4 extension. My code goes like : GLfloat vertices[] = { 0.5,0.25,1.0, 0.5,0.75,1.0, -0.5,0.75,1.0, -0.5,0.25,1.0, 0.6,0.35,1.0, 0.6,0.85,1.0, -0.6,0.85,1.0, -0.6,0.35,1.0 }; glProgramParameteriEXT(psId, GL_GEOMETRY_INPUT_TYPE_EXT, GL_TRIANGLES); glProgramParameteriEXT(psId, GL_GEOMETRY_OUTPUT_TYPE_EXT, GL_TRIANGLE_STRIP); glLinkProgram(psId); glBindAttribLocation(psId,0,"Position"); glEnableVertexAttribArray (0); glVertexAttribPointer(0, 3, GL_FLOAT, 0, 0, vertices); glDrawArrays(GL_TRIANGLE_STRIP,0,4); My vertex shader is : #version 150 in vec3 Position; void main() { gl_Position = vec4(Position,1.0); } Geometry shader is : #version 150 #extension GL_EXT_geometry_shader4 : enable in vec4 pos[3]; void main() { int i; vec4 vertex; gl_Position = pos[0]; EmitVertex(); gl_Position = pos[1]; EmitVertex(); gl_Position = pos[2]; EmitVertex(); gl_Position = pos[0] + vec4(0.3,0.0,0.0,0.0); EmitVertex(); EndPrimitive(); } Nothing is rendered with this code. What exactly should be the mode in glDrawArrays() ? How does the GL_GEOMETRY_OUTPUT_TYPE_EXT parameter will affect glDrawArrays() ? What I expect is 3 vertices will be passed on to Geometry Shader and using those we construct a primitive of size 4 (assuming GL_TRIANGLE_STRIP requires 4 vertices). Can somebody please throw some light on this ?

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• Alpha interpolation in a pixel shader

  - by c4sh

  How does the interpolation in a fragment shader work when it comes to the alpha parameter? I'm programming a shader with SharpDX, DirectX11. My idea is to interpolate 2 3d points of a segment, so that I'll have the position interpolated in between in the pixel shader. But I want to know what happens with the alpha parameter when that position is blocked by another polygon. For instance, if alpha is 1.0 at the left end of my segment and 0.0 at the other one. What is the value of alpha in the middle, 0.5? Or does it depend on the visibility at that point (meaning it could be, for instance, 1.0 OR 0.0 depending on if that part of the segment is hidden by a poolygon?

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• What vertex shader code should be used for a pixel shader used for simple 2D SpriteBatch drawing in XNA?

  - by Michael

  Preface First of all, why is a vertex shader required for a SilverlightEffect (.slfx file) in Silverlight 5? I'm trying to port a simple 2D XNA game to Silverlight 5 RC, and I would like to use a basic pixel shader. This shader works great in XNA for Windows and Xbox, but I can't get it to compile with Silverlight as a SilverlightEffect. The MS blog for the Silverlight Toolkit says that "there is no difference between .slfx and .fx", but apparently this isn't quite true -- or at least SpriteBatch is working some magic for us in "regular XNA", and it isn't in "Silverlight XNA". If I try to directly copy my pixel shader file into a Silverlight project (and change it to the supported "Effect - Silverlight" importer/processor), when I try to compile I see the following error message: Invalid effect file. Unable to find vertex shader in pass "P0" Indeed, there isn't a vertex shader in my pixel shader file. I haven't needed one with my other 2D XNA apps since I'm just doing basic SpriteBatch drawing. I tried adding a vertex shader to my shader file, using Remi Gillig's comment on this Shawn Hargreaves blog post for guidance, but it doesn't quite work. The shader file successfully compiles, and I see some semblance of my game on screen, but it's tiny, twisted, repeated, and all jumbled up. So clearly something's not quite right. The Real Question So that brings me to my real question: Since a vertex shader is required, is there a basic vertex shader function that works for simple 2D SpriteBatch drawing? And if the vertex shader requires world/view/project matricies as parameters, what values am I supposed to use for a 2D game? Can any shader pros help? Thanks!

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• Combine Two Shader Program

  - by Siddharth

  For my android application, I want to apply brightness and contrast shader on same image. At present I am using gpuimage plugin. In that I found two separate program for brightness and contrast as per the following. Contrast shader: varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform lowp float contrast; void main() { lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate); gl_FragColor = vec4(((textureColor.rgb - vec3(0.5)) * contrast + vec3(0.5)), textureColor.w); } Brightness shader: varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform lowp float brightness; void main() { lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate); gl_FragColor = vec4((textureColor.rgb + vec3(brightness)), textureColor.w); } Now applying both of the effects I write following code varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; varying highp vec2 textureCoordinate2; uniform sampler2D inputImageTexture2; uniform lowp float contrast; uniform lowp float brightness; void main() { lowp vec4 textureColorForContrast = texture2D(inputImageTexture, textureCoordinate); lowp vec4 contastVec4 = vec4(((textureColorForContrast.rgb - vec3(0.5)) * contrast + vec3(0.5)), textureColorForContrast.w); lowp vec4 textureColorForBrightness = texture2D(inputImageTexture2, textureCoordinate2); lowp vec4 brightnessVec4 = vec4((textureColorForBrightness.rgb + vec3(brightness)), textureColorForBrightness.w); gl_FragColor = contastVec4 + brightnessVec4; } Doesn't able to get desire result. I can't able to figure out what I have to do next? So please friends help me in this. What program I have to write?

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• Pixel Shader, YUV-RGB Conversion failing

  - by TomTom

  I am tasked with playing back a video hthat comes in in a YUV format as an overlay in a larger game. I am not a specialist in Direct3d, so I am struggling. I managed to get a shader working and am rendering 3 textures (Y, V, U). Sadly I am totally unable to get anything like a decent image. Documentation is also failing me. I am currently loading the different data planes (Y,V,U) in three different textures: m_Textures = new Texture[3]; // Y Plane m_Textures[0] = new Texture(m_Device, w, h, 1, Usage.None, Format.L8, Pool.Managed); // V Plane m_Textures[1] = new Texture(m_Device, w2, h2, 1, Usage.None, Format.L8, Pool.Managed); // U Plane m_Textures[2] = new Texture(m_Device, w2, h2, 1, Usage.None, Format.L8, Pool.Managed); When I am rendering them as R, G and B respectively with the following code: float4 Pixel( float2 texCoord: TEXCOORD0) : COLOR0 { float y = tex2D (ytexture, texCoord); float v = tex2D (vtexture, texCoord); float u = tex2D (utexture, texCoord); //R = Y + 1.140 (V -128) //G = Y - 0.395 (U-128) - 0.581 (V-128) //B = Y + 2.028 (U-128) float r = y; //y + 1.140 * v; float g = v; //y - 0.395 * u - 0.581 * v; float b = u; //y + 2.028 * u; float4 result; result.a = 255; result.r = r; //clamp (r, 0, 255); result.g = g; //clamp (g, 0, 255); result.b = b; //clamp (b, 0, 255); return result; } Then the resulting image is - quite funny. I can see the image, but colors are totally distorted, as it should be. The formula I should apply shows up in the comment of the pixel shader, but when I do it, the resulting image is pretty brutally magenta only. This gets me to the question - when I read out an L8 texture into a float, with float y = tex2D (ytexture, texCoord); what is the range of values? The "origin" values are 1 byte, 0 to 255, and the forum I have assumes this. Naturally I am totally off when the values returned are somehow normalized. My Clamp operation at the end also will fail if for example colors in a pixel shader are normalized 0 to 1. Anyone an idea how that works? Please point me also to documentation - I have not found anything in this regard.

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• cocos2dx - Custom Fragment Shader and CCRenderTexture

  - by saiy2k

  I have a CCRenderTexture that is filled with a sprite when the scene is loaded, as follows, canvas = CCRenderTexture::create(this->getContentSize().width, this->getContentSize().height); canvas->setPosition(data->position); canvas->beginWithClear(0.0, 0.0, 0.0, 0); this->visit(); canvas->end(); The above code is written within a class, which derives from CCSprite (Hence this). Then, in another function applyShader(), I create a sprite named splat, from the texture of CCRenderTexture *canvas. Thus splat will contain the whole texture of canvas. Now I apply a custom fragment shader to the splat by calling the function splat->renderShader(), which will modify some small portion of the whole texture. Then I draw the modified texture back to the CCRenderTexture *canvas. Hence, applyShader() will * take a texture from CCRenderTexture, * create a sprite based on it, * apply a fragment shader to it * and draw the modified texture back to CCRenderTexture. This applyShader() will be called repetitively and its code is as follows: splat = Splat::createWithTexture(art->canvas->getSprite()->getTexture()); splat->renderShader(); art->canvas->begin(); splat->visit(); art->canvas->end(); My shader code is (nothing fancy) precision mediump float; varying vec2 v_texCoord; uniform sampler2D u_texture; uniform sampler2D u_colorRampTexture; uniform float params[5]; void main() { gl_FragColor = texture2D(u_texture, v_texCoord); return; } So, with the above code I expect the original sprite this to get rendered over and over again without any visual changes. But on each call to applyShader(), the texture is getting stretched a little and the stretched image is getting rendered. After some 10 calls, the image gets so distorted. Can someone please tell me where I am going wrong? Thanks :-) PS: All code shown here is partial, not complete code. Edit: Adding Screens Update: The problem has nothing to do with shaders it seems. It happens even when I dont call renderShader(). The actual lines of code is: splat = Splat::createWithTexture(art->canvas->getSprite()->getTexture()); splat->setPosition( ccp( art->getContentSize().width * 0.5, art->getContentSize().height * 0.5 ) ); splat->setFlipY(true); art->canvas->begin(); splat->visit(); art->canvas->end();

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• Incorrect colour blending when using a pixel shader with XNA

  - by MazK

  I'm using XNA 4.0 to create a 2D game and while implementing a layer tinting pixel shader I noticed that when the texture's alpha value is anything between 1 or 0 the end result is different than expected. The tinting works from selecting a colour and setting the amount of tint. This is achieved via the shader which works out first the starting colour (for each r, g, b and a) : float red = texCoord.r * vertexColour.r; and then the final tinted colour : output.r = red + (tintColour.r - red) * tintAmount; The alpha value isn't tinted and is left as : output.a = texCoord.a * vertexColour.a; The picture in the link below shows different backdrops against an energy ball object where it's outer glow hasn't blended as I would like it to. The middle two are incorrect as the second non tinted one should not show a glow against a white BG and the third should be entirely invisible. The blending function is NonPremultiplied. Why the alpha value is interfering with the final colour?

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• Geometry Shader input vertices order

  - by NPS

  MSDN specifies (link) that when using triangleadj type of input to the GS, it should provide me with 6 vertices in specific order: 1st vertex of the triangle processed, vertex of an adjacent triangle, 2nd vertex of the triangle processed, another vertex of an adjacent triangle and so on... So if I wanted to create a pass-through shader (i.e. output the same triangle I got on input and nothing else) I should return vertices 0, 2 and 4. Is that correct? Well, apparently it isn't because I did just that and when I ran my app the vertices were flickering (like changing positions/disappearing/showing again or sth like that). But when I instead output vertices 0, 1 and 2 the app rendered the mesh correctly. I could provide some code but it seems like the problem is in the input vertices order, not the code itself. So what order do input vertices to the GS come in?

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• Fog shader camera problem

  - by MaT

  I have some difficulties with my vertex-fragment fog shader in Unity. I have a good visual result but the problem is that the gradient is based on the camera's position, it moves as the camera moves. I don't know how to fix it. Here is the shader code. struct v2f { float4 pos : SV_POSITION; float4 grabUV : TEXCOORD0; float2 uv_depth : TEXCOORD1; float4 interpolatedRay : TEXCOORD2; float4 screenPos : TEXCOORD3; }; v2f vert(appdata_base v) { v2f o; o.pos = mul(UNITY_MATRIX_MVP, v.vertex); o.uv_depth = v.texcoord.xy; o.grabUV = ComputeGrabScreenPos(o.pos); half index = v.vertex.z; o.screenPos = ComputeScreenPos(o.pos); o.interpolatedRay = mul(UNITY_MATRIX_MV, v.vertex); return o; } sampler2D _GrabTexture; float4 frag(v2f IN) : COLOR { float3 uv = UNITY_PROJ_COORD(IN.grabUV); float dpth = UNITY_SAMPLE_DEPTH(tex2Dproj(_CameraDepthTexture, uv)); dpth = LinearEyeDepth(dpth); float4 wsPos = (IN.screenPos + dpth * IN.interpolatedRay); // Here is the problem but how to fix it float fogVert = max(0.0, (wsPos.y - _Depth) * (_DepthScale * 0.1f)); fogVert *= fogVert; fogVert = (exp (-fogVert)); return fogVert; } Thanks a lot !

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• Strange if-else branching behavior in a fragment shader

  - by Winged

  In my fragment shader I have passed an uniform int uLightType variable, which indicates what type of light is in usage right now. The problem is that if-else branching does not work correctly - the fragment shader performs instructions in every if statement block. if (uLightType == 1) { // Spotlight light type vec3 depthTextureCoord = vDepthPosition.xyz / vDepthPosition.w; shadowDepth = unpack(texture2D(uDepthMapSampler, depthTextureCoord.xy)); } else if (uLightType == 2) { // Omni-directional light type shadowDepth = unpack(textureCube(uDepthCubemapSampler, -lightVec)); } In the case when uLightType equals 1, unless I comment out the content of the second if block, it assigns an another value to shadowDepth. Also while uLightType equals 1, when I remove the second 'if' block and change == to != like in the sample code below, nothing happens (which means that uLightType really equals 1). if (uLightType != 1) { // Spotlight light type vec3 depthTextureCoord = vDepthPosition.xyz / vDepthPosition.w; shadowDepth = unpack(texture2D(uDepthMapSampler, depthTextureCoord.xy)); } Also, when I manually create an int variable (which is not an uniform) like this: var lightType = 1; and replace uLightType with it in the if-else branch, everything works fine, so I guess it have something to do with the fact that uLightType is the uniform.

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• Toon/cel shading with variable line width?

  - by Nick Wiggill

  I see a few broad approaches out there to doing cel shading: Duplication & enlargement of model with flipped normals (not an option for me) Sobel filter / fragment shader approaches to edge detection Stencil buffer approaches to edge detection Geometry (or vertex) shader approaches that calculate face and edge normals Am I correct in assuming the geometry-centric approach gives the greatest amount of control over lighting and line thickness, as well eg. for terrain where you might see the silhouette line of a hill merging gradually into a plain? What if I didn't need pixel lighting on my terrain surfaces? (And I probably won't as I plan to use cell-based vertex- or texturemap-based lighting/shadowing.) Would I then be better off sticking with the geometry-type approach, or go for a screen space / fragment approach instead to keep things simpler? If so, how would I get the "inking" of hills within the mesh silhouette, rather than only the outline of the entire mesh (with no "ink" details inside that outline? Lastly, is it possible to cheaply emulate the flipped-normals approach, using a geometry shader? Is that exactly what the GS approaches do? What I want - varying line thickness with intrusive lines inside the silhouette... What I don't want...

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• Two pass blur shader using libgdx tile map renderer

  - by Alexandre GUIDET

  I am trying to apply the following technique: blur effect using two pass shader to my libgdx game using the OrthogonalTiledMapRenderer. The idea is to blur the background wich is also a tilemap but rendered with another camera with a different zoom applied. Here is a screen capture without effect: Using the OrthogonalTiledMapRenderer sprite batch like this: backgroundMapRenderer.getSpriteBatch().setShader(shaderBlurX); backgroundMapRenderer.render(layerBackground); I get the following render: Wich is ok for X blur pass. I then try using frame buffer object like in this example. But the effect seems to be too much zoomed: I may be messing up with the camera and the zoom factor. Here is the code: private ShaderProgram shaderBlurX; private ShaderProgram shaderBlurY; private int FBO_SIZE = 800; private FrameBuffer targetA; private FrameBuffer targetB; targetA = new FrameBuffer(Pixmap.Format.RGBA8888, FBO_SIZE, FBO_SIZE, false); targetB = new FrameBuffer(Pixmap.Format.RGBA8888, FBO_SIZE, FBO_SIZE, false); targetA.begin(); Gdx.gl.glClearColor(1, 1, 1, 0); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); backgroundMapRenderer.render(layerBackground); targetA.end(); targetB.begin(); Gdx.gl.glClearColor(1, 1, 1, 0); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); backgroundMapRenderer.getSpriteBatch().setShader(shaderBlurX); backgroundMapRenderer.render(layerBackground); targetB.end(); TextureRegion back = new TextureRegion(targetB.getColorBufferTexture()); back.flip(false, true); backgroundMapRenderer.getSpriteBatch() .setProjectionMatrix(backgroundCamera.combined); backgroundMapRenderer.getSpriteBatch().setShader(shaderBlurY); backgroundMapRenderer.getSpriteBatch().begin(); backgroundMapRenderer.getSpriteBatch().draw(back, 0, 0); backgroundMapRenderer.getSpriteBatch().end(); I know I am making something the wrong way, but I can't find any resources about applying two passes shader using tile map renderer. Does someone know how to achieve this?

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