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  • How can I pass an array of floats to the fragment shader using textures?

    - by James
    I want to map out a 2D array of depth elements for the fragment shader to use to check depth against to create shadows. I want to be able to copy a float array into the GPU, but using large uniform arrays causes segfaults in openGL so that is not an option. I tried texturing but the best i got was to use GL_DEPTH_COMPONENT glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, 512, 512, 0, GL_DEPTH_COMPONENT, GL_FLOAT, smap); Which doesn't work because that stores depth components (0.0 - 1.0) which I don't want because I have no idea how to calculate them using the depth value produced by the light sources MVP matrix multiplied by the coordinate of each vertex. Is there any way to store and access large 2D arrays of floats in openGL?

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  • How do I get FEATURE_LEVEL_9_3 to work with shaders in Direct3D11?

    - by Dominic
    Currently I'm going through some tutorials and learning DX11 on a DX10 machine (though I just ordered a new DX11 compatible computer) by means of setting the D3D_FEATURE_LEVEL_ setting to 10_0 and switching the vertex and pixel shader versions in D3DX11CompileFromFile to "vs_4_0" and "ps_4_0" respectively. This works fine as I'm not using any DX11-only features yet. I'd like to make it compatible with DX9.0c, which naively I thought I could do by changing the feature level setting to 9_3 or something and taking the vertex/pixel shader versions down to 3 or 2. However, no matter what I change the vertex/pixel shader versions to, it always fails when I try to call D3DX11CompileFromFile to compile the vertex/pixel shader files when I have D3D_FEATURE_LEVEL_9_3 enabled. Maybe this is due to the the vertex/pixel shader files themselves being incompatible for the lower vertex/pixel shader versions, but I'm not expert enough to say. My shader files are listed below: Vertex shader: cbuffer MatrixBuffer { matrix worldMatrix; matrix viewMatrix; matrix projectionMatrix; }; struct VertexInputType { float4 position : POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; PixelInputType LightVertexShader(VertexInputType input) { PixelInputType output; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; // Calculate the position of the vertex against the world, view, and projection matrices. output.position = mul(input.position, worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix); // Store the texture coordinates for the pixel shader. output.tex = input.tex; // Calculate the normal vector against the world matrix only. output.normal = mul(input.normal, (float3x3)worldMatrix); // Normalize the normal vector. output.normal = normalize(output.normal); return output; } Pixel Shader: Texture2D shaderTexture; SamplerState SampleType; cbuffer LightBuffer { float4 ambientColor; float4 diffuseColor; float3 lightDirection; float padding; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; float4 LightPixelShader(PixelInputType input) : SV_TARGET { float4 textureColor; float3 lightDir; float lightIntensity; float4 color; // Sample the pixel color from the texture using the sampler at this texture coordinate location. textureColor = shaderTexture.Sample(SampleType, input.tex); // Set the default output color to the ambient light value for all pixels. color = ambientColor; // Invert the light direction for calculations. lightDir = -lightDirection; // Calculate the amount of light on this pixel. lightIntensity = saturate(dot(input.normal, lightDir)); if(lightIntensity > 0.0f) { // Determine the final diffuse color based on the diffuse color and the amount of light intensity. color += (diffuseColor * lightIntensity); } // Saturate the final light color. color = saturate(color); // Multiply the texture pixel and the final diffuse color to get the final pixel color result. color = color * textureColor; return color; }

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  • Tessellation Texture Coordinates

    - by Stuart Martin
    Firstly some info - I'm using DirectX 11 , C++ and I'm a fairly good programmer but new to tessellation and not a master graphics programmer. I'm currently implementing a tessellation system for a terrain model, but i have reached a snag. My current system produces a terrain model from a height map complete with multiple texture coordinates, normals, binormals and tangents for rendering. Now when i was using a simple vertex and pixel shader combination everything worked perfectly but since moving to include a hull and domain shader I'm slightly confused and getting strange results. My terrain is a high detail model but the textured results are very large patches of solid colour. My current setup passes the model data into the vertex shader then through the hull into the domain and then finally into the pixel shader for use in rendering. My only thought is that in my hull shader i pass the information into the domain shader per patch and this is producing the large areas of solid colour because each patch has identical information. Lighting and normal data are also slightly off but not as visibly as texturing. Below is a copy of my hull shader that does not work correctly because i think the way that i am passing the data through is incorrect. If anyone can help me out but suggesting an alternative way to get the required data into the pixel shader? or by showing me the correct way to handle the data in the hull shader id be very thankful! cbuffer TessellationBuffer { float tessellationAmount; float3 padding; }; struct HullInputType { float3 position : POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; float3 tangent : TANGENT; float3 binormal : BINORMAL; float2 tex2 : TEXCOORD1; }; struct ConstantOutputType { float edges[3] : SV_TessFactor; float inside : SV_InsideTessFactor; }; struct HullOutputType { float3 position : POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; float3 tangent : TANGENT; float3 binormal : BINORMAL; float2 tex2 : TEXCOORD1; float4 depthPosition : TEXCOORD2; }; ConstantOutputType ColorPatchConstantFunction(InputPatch<HullInputType, 3> inputPatch, uint patchId : SV_PrimitiveID) { ConstantOutputType output; output.edges[0] = tessellationAmount; output.edges[1] = tessellationAmount; output.edges[2] = tessellationAmount; output.inside = tessellationAmount; return output; } [domain("tri")] [partitioning("integer")] [outputtopology("triangle_cw")] [outputcontrolpoints(3)] [patchconstantfunc("ColorPatchConstantFunction")] HullOutputType ColorHullShader(InputPatch<HullInputType, 3> patch, uint pointId : SV_OutputControlPointID, uint patchId : SV_PrimitiveID) { HullOutputType output; output.position = patch[pointId].position; output.tex = patch[pointId].tex; output.tex2 = patch[pointId].tex2; output.normal = patch[pointId].normal; output.tangent = patch[pointId].tangent; output.binormal = patch[pointId].binormal; return output; } Edited to include the domain shader:- [domain("tri")] PixelInputType ColorDomainShader(ConstantOutputType input, float3 uvwCoord : SV_DomainLocation, const OutputPatch<HullOutputType, 3> patch) { float3 vertexPosition; PixelInputType output; // Determine the position of the new vertex. vertexPosition = uvwCoord.x * patch[0].position + uvwCoord.y * patch[1].position + uvwCoord.z * patch[2].position; output.position = mul(float4(vertexPosition, 1.0f), worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix); output.depthPosition = output.position; output.tex = patch[0].tex; output.tex2 = patch[0].tex2; output.normal = patch[0].normal; output.tangent = patch[0].tangent; output.binormal = patch[0].binormal; return output; }

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  • Getting FEATURE_LEVEL_9_3 to work in DX11

    - by Dominic
    Currently I'm going through some tutorials and learning DX11 on a DX10 machine (though I just ordered a new DX11 compatible computer) by means of setting the D3D_FEATURE_LEVEL_ setting to 10_0 and switching the vertex and pixel shader versions in D3DX11CompileFromFile to "vs_4_0" and "ps_4_0" respectively. This works fine as I'm not using any DX11-only features yet. I'd like to make it compatible with DX9.0c, which naively I thought I could do by changing the feature level setting to 9_3 or something and taking the vertex/pixel shader versions down to 3 or 2. However, no matter what I change the vertex/pixel shader versions to, it always fails when I try to call D3DX11CompileFromFile to compile the vertex/pixel shader files when I have D3D_FEATURE_LEVEL_9_3 enabled. Maybe this is due to the the vertex/pixel shader files themselves being incompatible for the lower vertex/pixel shader versions, but I'm not expert enough to say. My shader files are listed below: Vertex shader: cbuffer MatrixBuffer { matrix worldMatrix; matrix viewMatrix; matrix projectionMatrix; }; struct VertexInputType { float4 position : POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; PixelInputType LightVertexShader(VertexInputType input) { PixelInputType output; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; // Calculate the position of the vertex against the world, view, and projection matrices. output.position = mul(input.position, worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix); // Store the texture coordinates for the pixel shader. output.tex = input.tex; // Calculate the normal vector against the world matrix only. output.normal = mul(input.normal, (float3x3)worldMatrix); // Normalize the normal vector. output.normal = normalize(output.normal); return output; } Pixel Shader: Texture2D shaderTexture; SamplerState SampleType; cbuffer LightBuffer { float4 ambientColor; float4 diffuseColor; float3 lightDirection; float padding; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; float4 LightPixelShader(PixelInputType input) : SV_TARGET { float4 textureColor; float3 lightDir; float lightIntensity; float4 color; // Sample the pixel color from the texture using the sampler at this texture coordinate location. textureColor = shaderTexture.Sample(SampleType, input.tex); // Set the default output color to the ambient light value for all pixels. color = ambientColor; // Invert the light direction for calculations. lightDir = -lightDirection; // Calculate the amount of light on this pixel. lightIntensity = saturate(dot(input.normal, lightDir)); if(lightIntensity > 0.0f) { // Determine the final diffuse color based on the diffuse color and the amount of light intensity. color += (diffuseColor * lightIntensity); } // Saturate the final light color. color = saturate(color); // Multiply the texture pixel and the final diffuse color to get the final pixel color result. color = color * textureColor; return color; }

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  • OpenGL CPU vs. GPU

    - by Nitrex88
    So I've always been under the impression that doing work on the GPU is always faster than on the CPU. Because of this, in OpenGL, I usually try to do intensive tasks in shaders so they get the speed boost from the GPU. However, now I'm starting to realize that some things simply work better on the CPU and actually perform worse on the GPU (particularly when a geometry shader is involved). For example, in a recent project I did involving procedurally generated terrain, I tried passing a grid of single triangles into a geometry shader, and tesselated each of these triangles into quads with 400 vertices whose height was determined by a noise function. This worked fine, and looked great, but easily maxed out the GPU with only 25 base triangles and caused a very slow framerate. I then discovered that tesselating on the CPU instead, and setting the height (using noise function) in the vertex shader was actually faster! This prompted me to question the benefits of using the GPU as much as possible... So, I was wondering if someone could describe the general pros and cons of using the GPU vs CPU for intensive graphics tasks. I know this mainly comes down to what your trying to achieve, so if necessary, use the above scenario to discuss why the "CPU + vertex shader" was actually faster than doing everything in the geometry shader on the GPU. It's possible my hardware (newest macbook pro) isn't optomized well for the geometry shader (thus causing the slow framerate). Also, I read that the vertex shader is very good with parallelism, and would love a quick explanation of how this may have played a role in speeding up my procedural terrain. Any info/advice about CPU/GPU/shaders would be awesome!

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  • OpenGL CPU vs. GPU

    - by Nitrex88
    So I've always been under the impression that doing work on the GPU is always faster than on the CPU. Because of this, in OpenGL, I usually try to do intensive tasks in shaders so they get the speed boost from the GPU. However, now I'm starting to realize that some things simply work better on the CPU and actually perform worse on the GPU (particularly when a geometry shader is involved). For example, in a recent project I did involving procedurally generated terrain, I tried passing a grid of single triangles into a geometry shader, and tesselated each of these triangles into quads with 400 vertices whose height was determined by a noise function. This worked fine, and looked great, but easily maxed out the GPU with only 25 base triangles and caused a very slow framerate. I then discovered that tesselating on the CPU instead, and setting the height (using noise function) in the vertex shader was actually faster! This prompted me to question the benefits of using the GPU as much as possible... So, I was wondering if someone could describe the general pros and cons of using the GPU vs CPU for intensive graphics tasks. I know this mainly comes down to what your trying to achieve, so if necessary, use the above scenario to discuss why the "CPU + vertex shader" was actually faster than doing everything in the geometry shader on the GPU. It's possible my hardware (newest macbook pro) isn't optomized well for the geometry shader (thus causing the slow framerate). Also, I read that the vertex shader is very good with parallelism, and would love a quick explanation of how this may have played a role in speeding up my procedural terrain. Any info/advice about CPU/GPU/shaders would be awesome!

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  • My GLSL shader isn't compiling even though it should. What should I investigate?

    - by reapz
    I'm porting an iOS game to Android. One of the shaders I'm using wouldn't compile until I reduced the number of uniform variables. Here are the uniform definitions: uniform highp mat4 ViewProjMatrix; uniform mediump vec3 LightDirWorld; uniform mediump int BoneCount; uniform highp mat4 BoneMatrixArray[8]; uniform highp mat3 BoneMatrixArrayIT[8]; uniform mediump int LightCount; uniform mediump vec3 LightPos[4]; // This used to be 12, but now 4, next lines also uniform lowp vec3 LightColour[4]; uniform mediump vec3 LightInnerOuterFalloff[4]; My issue is that the GLSL shader wouldn't compile until I reduced the count of the above arrays from 12 to 4. My understanding is that if those 3 lines were arrays of 12 then I would be using 56 vertex uniform vectors. I query the system at startup (GL_MAX_VERTEX_UNIFORM_VECTORS) and it says that 128 are available. Why wouldn't it compile with 56? I'm having issues on the Kindle Fire.

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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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  • GLEW + VS2010 error

    - by Egon
    Hi folks, I am running into this issue and don't know what to do ? 'abc.exe': Loaded 'D:\Windows\SysWOW64\nvoglv32.dll', Cannot find or open the PDB file earlier I was getting a whole bunch of errors, but the microsoft symbols source set the issue for all of them except this one file : nvoglv32.dll ; does anybody know how I can resolve this issue or get my hands on the file "nvoglv32.pdb" ? Thanks -A

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  • How would I create this background effect?

    - by William
    What would you call the effect applied to the backgrounds in the Giygas fight of Earthbound, and the battle backgrounds in Mother 3? This is what I'm talking about. http://www.youtube.com/watch?v=tcaErqaoWek http://www.youtube.com/watch?v=ubVnmeTRqhg Now anyone know how I could go about this without using animated images, or using openGL?

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  • changing the intensity of lighten/darken on bitmaps using PorterDuffXfermode in the Android Paint class

    - by user1116836
    Ok my orignal question has changed. How do i change the intensity of how something like this is effected? DayToNight.setXfermode(new PorterDuffXfermode(Mode.DST_IN)); in my dream world it would have worked like this DayToNight.setXfermode(new PorterDuffXfermode(Mode.DST_IN(10))); the 10 being a level of intensity. An example would be if I had a flickering candle, when the candle burns bright I want the bitmaps I am drawing to the screen to retain their origanol color and brightness, when it flickers I want the bitmaps to be almost blacked out, and I want to darken the Bitmaps as the light dims. I have equations, timers and all that figured out, just not how to actually apply it to change the color/brightness. Maybe burning the images is what im looking for? I just want to change the lightness lol. I feel like using paint.setShader might be a solution, but the information in this area is pretty limited from what i have been able to find. Any help would be appreciated. edit: to be crystal clear, i am looking for a way to lighten/darken bitmaps as I draw them to the canvas

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  • I'm looking for a blend mode that gives 'realistic' paint colors. (Subtractive)

    - by almosnow
    I've been looking for a blend mode to (well ...) blend two RGB pixels in order to build colors in the samw way that a painter builds them (i.e: subtractive). Here are quick examples of the type of results that I'm expecting: CYAN + MAGENTA = BLUE CYAN + YELLOW = GREEN MAGENTA + YELLOW = RED RED + YELLOW = ORANGE RED + BLUE = PURPLE YELLOW + BLUE = GREEN I'm looking for a formula, like: dest_red = first_red + second_red; dest_green = first_green + second_green; dest_blue = first_blue + second_blue; I've tried with the commonly used 'multiply' formula but it doesn't work; I've tried with custom made formulas but I'm still not able to 'crack' how it should work. And I know already a lot of color theory so please refrain from answers like: Check this link: http://the_difference_betweeen_additive_and_subtractive_lightning.html

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  • Windows Azure HPC Scheduler Architecture

    - by Churianov Roman
    So far I've found very little information on the scheduling policy, resource management policy of Azure HPC Scheduler. I would appreciate any kind of information regarding some of these questions: What scheduling policy does a Head Node use to scatter jobs to Compute Nodes? Does Azure Scheduler use prior information about the jobs (compute time, memory demands ...) ? If 'yes', how it gets this information? Does Azure Scheduler split a job into several parallel jobs on one Compute node? Does it have any protection from Compute Node failures? (what it does when a compute node stops responding) Does it support addition/subtraction of Compute nodes? Is it possible to cancel a job? P.S. I'm aware of the MSDN resource Windows Azure HPC Scheduler. I found only information of how to use this Scheduler but almost nothing about how it works inside.

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  • GLSL - one-pass gaussian blur

    - by martin pilch
    It is possible to implement fragment shader to do one-pass gaussian blur? I have found lot of implementation of two-pass blur (gaussian and box blur): http://callumhay.blogspot.com/2010/09/gaussian-blur-shader-glsl.html http://www.gamerendering.com/2008/10/11/gaussian-blur-filter-shader/ http://www.geeks3d.com/20100909/shader-library-gaussian-blur-post-processing-filter-in-glsl/ and so on. I have been thinking of implementing gaussian blur as convolution (in fact, it is the convolution, the examples above are just aproximations): http://en.wikipedia.org/wiki/Gaussian_blur

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  • Using Ogre particle point billboards with shaders

    - by Jay
    I'm learning about using Ogre particles and had some questions about how the point type particles work. Q. I believe point type particles are implemented as a single position. Is one single vertex is passed to the vertex shader? Q. If one vertex is passed to the vertex shader then what gets sent to the fragment shader? Q. Can I pass the particle size to the shader? Perhaps with a custom parameter?

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  • GLSL compiler messages from different vendors [on hold]

    - by revers
    I'm writing a GLSL shader editor and I want to parse GLSL compiler messages to make hyperlinks to invalid lines in a shader code. I know that these messages are vendor specific but currently I have access only to AMD's video cards. I want to handle at least NVidia's and Intel's hardware, apart from AMD's. If you have video card from different vendor than AMD, could you please give me the output of following C++ program: #include <GL/glew.h> #include <GL/freeglut.h> #include <iostream> using namespace std; #define STRINGIFY(X) #X static const char* fs = STRINGIFY( out vec4 out_Color; mat4 m; void main() { vec3 v3 = vec3(1.0); vec2 v2 = v3; out_Color = vec4(5.0 * v2.x, 1.0); vec3 k = 3.0; float = 5; } ); static const char* vs = STRINGIFY( in vec3 in_Position; void main() { vec3 v(5); gl_Position = vec4(in_Position, 1.0); } ); void printShaderInfoLog(GLint shader) { int infoLogLen = 0; int charsWritten = 0; GLchar *infoLog; glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLogLen); if (infoLogLen > 0) { infoLog = new GLchar[infoLogLen]; glGetShaderInfoLog(shader, infoLogLen, &charsWritten, infoLog); cout << "Log:\n" << infoLog << endl; delete [] infoLog; } } void printProgramInfoLog(GLint program) { int infoLogLen = 0; int charsWritten = 0; GLchar *infoLog; glGetProgramiv(program, GL_INFO_LOG_LENGTH, &infoLogLen); if (infoLogLen > 0) { infoLog = new GLchar[infoLogLen]; glGetProgramInfoLog(program, infoLogLen, &charsWritten, infoLog); cout << "Program log:\n" << infoLog << endl; delete [] infoLog; } } void initShaders() { GLuint v = glCreateShader(GL_VERTEX_SHADER); GLuint f = glCreateShader(GL_FRAGMENT_SHADER); GLint vlen = strlen(vs); GLint flen = strlen(fs); glShaderSource(v, 1, &vs, &vlen); glShaderSource(f, 1, &fs, &flen); GLint compiled; glCompileShader(v); bool succ = true; glGetShaderiv(v, GL_COMPILE_STATUS, &compiled); if (!compiled) { cout << "Vertex shader not compiled." << endl; succ = false; } printShaderInfoLog(v); glCompileShader(f); glGetShaderiv(f, GL_COMPILE_STATUS, &compiled); if (!compiled) { cout << "Fragment shader not compiled." << endl; succ = false; } printShaderInfoLog(f); GLuint p = glCreateProgram(); glAttachShader(p, v); glAttachShader(p, f); glLinkProgram(p); glUseProgram(p); printProgramInfoLog(p); if (!succ) { exit(-1); } delete [] vs; delete [] fs; } int main(int argc, char* argv[]) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA); glutInitWindowSize(600, 600); glutCreateWindow("Triangle Test"); glewInit(); GLenum err = glewInit(); if (GLEW_OK != err) { cout << "glewInit failed, aborting." << endl; exit(1); } cout << "Using GLEW " << glewGetString(GLEW_VERSION) << endl; const GLubyte* renderer = glGetString(GL_RENDERER); const GLubyte* vendor = glGetString(GL_VENDOR); const GLubyte* version = glGetString(GL_VERSION); const GLubyte* glslVersion = glGetString(GL_SHADING_LANGUAGE_VERSION); GLint major, minor; glGetIntegerv(GL_MAJOR_VERSION, &major); glGetIntegerv(GL_MINOR_VERSION, &minor); cout << "GL Vendor : " << vendor << endl; cout << "GL Renderer : " << renderer << endl; cout << "GL Version : " << version << endl; cout << "GL Version : " << major << "." << minor << endl; cout << "GLSL Version : " << glslVersion << endl; initShaders(); return 0; } On my video card it gives: Status: Using GLEW 1.7.0 GL Vendor : ATI Technologies Inc. GL Renderer : ATI Radeon HD 4250 GL Version : 3.3.11631 Compatibility Profile Context GL Version : 3.3 GLSL Version : 3.30 Vertex shader not compiled. Log: Vertex shader failed to compile with the following errors: ERROR: 0:1: error(#132) Syntax error: '5' parse error ERROR: error(#273) 1 compilation errors. No code generated Fragment shader not compiled. Log: Fragment shader failed to compile with the following errors: WARNING: 0:1: warning(#402) Implicit truncation of vector from size 3 to size 2. ERROR: 0:1: error(#174) Not enough data provided for construction constructor WARNING: 0:1: warning(#402) Implicit truncation of vector from size 1 to size 3. ERROR: 0:1: error(#132) Syntax error: '=' parse error ERROR: error(#273) 2 compilation errors. No code generated Program log: Vertex and Fragment shader(s) were not successfully compiled before glLinkProgram() was called. Link failed. Or if you like, you could give me other compiler messages than proposed by me. To summarize, the question is: What are GLSL compiler messages formats (INFOs, WARNINGs, ERRORs) for different vendors? Please give me examples or pattern explanation. EDIT: Ok, it seems that this question is too broad, then shortly: How does NVidia's and Intel's GLSL compilers present ERROR and WARNING messages? AMD/ATI uses patterns like this: ERROR: <position>:<line_number>: <message> WARNING: <position>:<line_number>: <message> (examples are above).

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  • Do you know of a C macro to compute Unix time and date?

    - by Alexis Wilke
    I'm wondering if someone knows/has a C macro to compute a static Unix time from a hard coded date and time as in: time_t t = UNIX_TIMESTAMP(2012, 5, 10, 9, 26, 13); I'm looking into that because I want to have a numeric static timestamp. This will be done hundred of times throughout the software, each time with a different date, and I want to make sure it is fast because it will run hundreds of times every second. Converting dates that many times would definitively slow down things (i.e. calling mktime() is slower than having a static number compiled in place, right?) [made an update to try to render this paragraph clearer, Nov 23, 2012] Update I want to clarify the question with more information about the process being used. As my server receives requests, for each request, it starts a new process. That process is constantly updated with new plugins and quite often such updates require a database update. Those must be run only once. To know whether an update is necessary, I want to use a Unix date (which is better than using a counter because a counter is much more likely to break once in a while.) The plugins will thus receive an update signal and have their on_update() function called. There I want to do something like this: void some_plugin::on_update(time_t last_update) { if(last_update < UNIX_TIMESTAMP(2010, 3, 22, 20, 9, 26)) { ...run update... } if(last_update < UNIX_TIMESTAMP(2012, 5, 10, 9, 26, 13)) { ...run update... } // as many test as required... } As you can see, if I have to compute the unix timestamp each time, this could represent thousands of calls per process and if you receive 100 hits a second x 1000 calls, you wasted 100,000 calls when you could have had the compiler compute those numbers once at compile time. Putting the value in a static variable is of no interest because this code will run once per process run. Note that the last_update variable changes depending on the website being hit (it comes from the database.) Code Okay, I got the code now: // helper (Days in February) #define _SNAP_UNIX_TIMESTAMP_FDAY(year) \ (((year) % 400) == 0 ? 29LL : \ (((year) % 100) == 0 ? 28LL : \ (((year) % 4) == 0 ? 29LL : \ 28LL))) // helper (Days in the year) #define _SNAP_UNIX_TIMESTAMP_YDAY(year, month, day) \ ( \ /* January */ static_cast<qint64>(day) \ /* February */ + ((month) >= 2 ? 31LL : 0LL) \ /* March */ + ((month) >= 3 ? _SNAP_UNIX_TIMESTAMP_FDAY(year) : 0LL) \ /* April */ + ((month) >= 4 ? 31LL : 0LL) \ /* May */ + ((month) >= 5 ? 30LL : 0LL) \ /* June */ + ((month) >= 6 ? 31LL : 0LL) \ /* July */ + ((month) >= 7 ? 30LL : 0LL) \ /* August */ + ((month) >= 8 ? 31LL : 0LL) \ /* September */+ ((month) >= 9 ? 31LL : 0LL) \ /* October */ + ((month) >= 10 ? 30LL : 0LL) \ /* November */ + ((month) >= 11 ? 31LL : 0LL) \ /* December */ + ((month) >= 12 ? 30LL : 0LL) \ ) #define SNAP_UNIX_TIMESTAMP(year, month, day, hour, minute, second) \ ( /* time */ static_cast<qint64>(second) \ + static_cast<qint64>(minute) * 60LL \ + static_cast<qint64>(hour) * 3600LL \ + /* year day (month + day) */ (_SNAP_UNIX_TIMESTAMP_YDAY(year, month, day) - 1) * 86400LL \ + /* year */ (static_cast<qint64>(year) - 1970LL) * 31536000LL \ + ((static_cast<qint64>(year) - 1969LL) / 4LL) * 86400LL \ - ((static_cast<qint64>(year) - 1901LL) / 100LL) * 86400LL \ + ((static_cast<qint64>(year) - 1601LL) / 400LL) * 86400LL ) WARNING: Do not use these macros to dynamically compute a date. It is SLOWER than mktime(). This being said, if you have a hard coded date, then the compiler will compute the time_t value at compile time. Slower to compile, but faster to execute over and over again.

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  • GLSL subroutine not being used

    - by amoffat
    I'm using a gaussian blur fragment shader. In it, I thought it would be concise to include 2 subroutines: one for selecting the horizontal texture coordinate offsets, and another for the vertical texture coordinate offsets. This way, I just have one gaussian blur shader to manage. Here is the code for my shader. The {{NAME}} bits are template placeholders that I substitute in at shader compile time: #version 420 subroutine vec2 sample_coord_type(int i); subroutine uniform sample_coord_type sample_coord; in vec2 texcoord; out vec3 color; uniform sampler2D tex; uniform int texture_size; const float offsets[{{NUM_SAMPLES}}] = float[]({{SAMPLE_OFFSETS}}); const float weights[{{NUM_SAMPLES}}] = float[]({{SAMPLE_WEIGHTS}}); subroutine(sample_coord_type) vec2 vertical_coord(int i) { return vec2(0.0, offsets[i] / texture_size); } subroutine(sample_coord_type) vec2 horizontal_coord(int i) { //return vec2(offsets[i] / texture_size, 0.0); return vec2(0.0, 0.0); // just for testing if this subroutine gets used } void main(void) { color = vec3(0.0); for (int i=0; i<{{NUM_SAMPLES}}; i++) { color += texture(tex, texcoord + sample_coord(i)).rgb * weights[i]; color += texture(tex, texcoord - sample_coord(i)).rgb * weights[i]; } } Here is my code for selecting the subroutine: blur_program->start(); blur_program->set_subroutine("sample_coord", "vertical_coord", GL_FRAGMENT_SHADER); blur_program->set_int("texture_size", width); blur_program->set_texture("tex", *deferred_output); blur_program->draw(); // draws a quad for the fragment shader to run on and: void ShaderProgram::set_subroutine(constr name, constr routine, GLenum target) { GLuint routine_index = glGetSubroutineIndex(id, target, routine.c_str()); GLuint uniform_index = glGetSubroutineUniformLocation(id, target, name.c_str()); glUniformSubroutinesuiv(target, 1, &routine_index); // debugging int num_subs; glGetActiveSubroutineUniformiv(id, target, uniform_index, GL_NUM_COMPATIBLE_SUBROUTINES, &num_subs); std::cout << uniform_index << " " << routine_index << " " << num_subs << "\n"; } I've checked for errors, and there are none. When I pass in vertical_coord as the routine to use, my scene is blurred vertically, as it should be. The routine_index variable is also 1 (which is weird, because vertical_coord subroutine is the first listed in the shader code...but no matter, maybe the compiler is switching things around) However, when I pass in horizontal_coord, my scene is STILL blurred vertically, even though the value of routine_index is 0, suggesting that a different subroutine is being used. Yet the horizontal_coord subroutine explicitly does not blur. What's more is, whichever subroutine comes first in the shader, is the subroutine that the shader uses permanently. Right now, vertical_coord comes first, so the shader blurs vertically always. If I put horizontal_coord first, the scene is unblurred, as expected, but then I cannot select the vertical_coord subroutine! :) Also, the value of num_subs is 2, suggesting that there are 2 subroutines compatible with my sample_coord subroutine uniform. Just to re-iterate, all of my return values are fine, and there are no glGetError() errors happening. Any ideas?

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  • Using a single texture image unit with multiple sampler uniforms

    - by bcrist
    I am writing a batching system which tracks currently bound textures in order to avoid unnecessary glBindTexture() calls. I'm not sure if I need to keep track of which textures have already been used by a particular batch so that if a texture is used twice, it will be bound to a different TIU for the second sampler which requires it. Is it acceptable for an OpenGL application to use the same texture image unit for multiple samplers within the same shader stage? What about samplers in different shader stages? For example: Fragment shader: ... uniform sampler2D samp1; uniform sampler2D samp2; void main() { ... } Main program: ... glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, tex_id); glUniform1i(samp1_location, 0); glUniform1i(samp2_location, 0); ... I don't see any reason why this shouldn't work, but what about if the shader program also included a vertex shader like this: Vertex shader: ... uniform sampler2D samp1; void main() { ... } In this case, OpenGL is supposed to treat both instances of samp1 as the same variable, and exposes a single location for them. Therefore, the same texture unit is being used in the vertex and fragment shaders. I have read that using the same texture in two different shader stages counts doubly against GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS but this would seem to contradict that. In a quick test on my hardware (HD 6870), all of the following scenarios worked as expected: 1 TIU used for 2 sampler uniforms in same shader stage 1 TIU used for 1 sampler uniform which is used in 2 shader stages 1 TIU used for 2 sampler uniforms, each occurring in a different stage. However, I don't know if this is behavior that I should expect on all hardware/drivers, or if there are performance implications.

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  • How do multipass shaders work in OpenGL?

    - by Boreal
    In Direct3D, multipass shaders are simple to use because you can literally define passes within a program. In OpenGL, it seems a bit more complex because it is possible to give a shader program as many vertex, geometry, and fragment shaders as you want. A popular example of a multipass shader is a toon shader. One pass does the actual cel-shading effect and the other creates the outline. If I have two vertex shaders, "cel.vert" and "outline.vert", and two fragment shaders, "cel.frag" and "outline.frag" (similar to the way you do it in HLSL), how can I combine them to create the full toon shader? I don't want you saying that a geometry shader can be used for this because I just want to know the theory behind multipass GLSL shaders ;)

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  • Shadowmap first phase and shaders

    - by KaiserJohaan
    I am using OpenGL 3.3 and am tryin to implement shadow mapping using cube maps. I have a framebuffer with a depth attachment and a cube map texture. My question is how to design the shaders for the first pass, when creating the shadowmap. This is my vertex shader: in vec3 position; uniform mat4 lightWVP; void main() { gl_Position = lightWVP * vec4(position, 1.0); } Now, do I even need a fragment shader in this shader pass? from what I understand after reading http://www.opengl.org/wiki/Fragment_Shader, by default gl_FragCoord.z is written to the currently attached depth component (to which my cubemap texture is bound to). Thus I shouldnt even need a fragment shader for this pass and from what I understand, there is no other work to do in the fragment shader other than writing this value. Is this correct?

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  • Differences in cg shader code for OpenGL vs. for DirectX?

    - by Cray
    I have been trying to use an existing library that automatically generates shaders (Hydrax plugin for Ogre3D). These shaders are used to render water and somewhat involved, but are not extremely complicated. However there seems to be some differences in how the cg shaders are handled by OpenGL and DirectX, more specifically, I am pretty sure that the author of the library only has debugged all the shaders for DirectX, and they work flawlessly there, but not so in OpenGL. There are no compiler errors, but the result just doesn't look the same. (And I have to run the library in OpenGL.) Isn't cg supposed to be a language that can freely use the exact same code for both platforms? Are there any specific known caveats one should know about when using the same code for them? Are there any fast ways to find what parts of the code work differently? (I am pretty sure that the shaders are the problem. Otherwise Ogre3D has great support for both problems, and everything is abstracted away nicely. Other shaders work in OpenGL, etc...)

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