• Advertisement
Sign in to follow this  

OpenGL Trouble with uniform matrices

This topic is 1023 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I've begun creating my own matrix stack to get away from legacy opengl.

I'm having some difficulty with setting up a GLSL vertex shader to take two uniform matrices. 

I currently have a working shader that takes a single uniform matrix (a full ModelViewProjection matrix) and renders my object correctly.

When I attempt to split out  that matrix into its Projection and ModelView Matrices and pass them in, the scene does not render.

--------------------------------------------------------------------

#version 330 
 
uniform mat4 uProjection;
uniform mat4 uModelView;
 
 
in vec3 v;
in vec3 vt;
in vec3 vn;
 
smooth out vec3 out_vn;
smooth out vec3 out_vt;
smooth out float depth;
 
void main(){
gl_Position = uProjection * uModelView * vec4(v,1);
out_vn = (uModelView * vec4(vn,0)).xyz;
out_vt = vt;
depth = gl_Position.z;
}
----------------------------------------------------------------------
uProjection is calculated just before glUniformMatrix is called (the projection is equivalent to glFrustum).
uModelview is  the product of three matrices:  Translation(0,0,-8) * Rotation(r,1,1,0) * Rotation(-.5f,-.5f,-.5f);

 

Is there anything special about using more than one uniform matrix input?

Share this post


Link to post
Share on other sites
Advertisement


Is there anything special about using more than one uniform matrix input?

 

Not really, it's pretty common...

 

Can you show us some client side code? Are both your calls to glUniformMatrix4fv() correct?

Share this post


Link to post
Share on other sites

The only real gotcha is to watch your glGetUniformLocation calls, making sure that they're returing valid locations and that you use these location in your subsequent glUniform calls.

Share this post


Link to post
Share on other sites

I *think* my glUniformMatrix4fv calls are correct. My program has a class called 'ShaderProgram' which I use to spin up shaders, bind attributes, and get uniform locations. The object itself queries each uniform location ONCE and stores it in its own lookup table. It has a helper function that lets me update my matrix uniforms, referencing them by name.

 

I've stumbled upon some extra wierdness fiddling with this thing. In transitioning to the 2-matrix scheme I have set uProjection to the Identity matrix and uModelView to (Frustum x Translate x Rotate x Translate), and I set the vertex shader to set gl_Position = uProjection x uModelView x v_in. This works, but if I switch the values of uModelView and uProjection, only some faces show. This is extreemly odd since one matrix is just an Identity matrix and shouldn't really affect the output. (in other words, for Matrices M and I, I expect to see MxI=IxM, but that is not the case for some reason).

 

 

----------------------Shader Initialization Snippet:--------------------------

GL20.glAttachShader(program_id, vertex_shader_id);
GL20.glAttachShader(program_id, fragment_shader_id);
GL20.glLinkProgram(program_id);
 
// Delete Shader objects
GL20.glDeleteShader(vertex_shader_id);
GL20.glDeleteShader(fragment_shader_id);
// Get Uniform Locations
if (uniforms != null) {//Check if uniform locations are needed
Uniform_Location.clear();//Clear old uniform locations. needed if program is being recreated
for (int i = 0; i < uniforms.length; i++) {// For each uniform name get its location and store it in a lookup table.
Uniform_Location.put(uniforms[i], GL20.glGetUniformLocation(program_id, uniforms[i]));
}
}

 

--------------glUniformMatrix4f usage-------------------------------

 
ByteBuffer matrix_buffer = ByteBuffer.allocateDirect(64).order(ByteOrder.nativeOrder()); //JAVA DIRECT NIO BUFFER, for use with LWJGL
 
public void UniformMatrix(String name, float[] m) {
Integer location = Uniform_Location.get(name);//Lookup uniform location from table
if (location != null) {
matrix_buffer.clear();//Restart write at beginning of buffer
matrix_buffer.asFloatBuffer().put(m).flip(); //Write to buffer and set its capacity
GL20.glUniformMatrix4f(location, 1, false, matrix_buffer);//Send the matrix data to opengl
}
return;
}

Share this post


Link to post
Share on other sites

I've just come to the realization that I am an idiot and shouldn't be writing shaders. This is a very profound feeling.mellow.png

 

My Vertex Shader was fine. My client code was fine. My fragment shader was varying the intensity of colors by the dot product of their normal and the forward vector, setting alpha to 0.

 

Thank you gentlemen for your help.biggrin.png

Share this post


Link to post
Share on other sites
Only by seeing our own limitations can we overcome them.

Keep at it!

Share this post


Link to post
Share on other sites

ByteBuffer matrix_buffer = ByteBuffer.allocateDirect(64).order(ByteOrder.nativeOrder()); //JAVA DIRECT NIO BUFFER, for use with LWJGL

 

and

 

matrix_buffer.asFloatBuffer().put(m).flip(); //Write to buffer and set its capacity

 

Be careful with what you're doing there. You'll be uploading data to the GPU all the time, you should strive for it to be a garbageless process. There you're creating two new objects each call is made. Moreover, timely deallocation of direct buffers isnt guaranteed, and you're doing a new direct buffer alloc each time.

 

You can very easily just create one instance of a big enough buffer and pass that all around the renderer, with LWJGL 3 you dont even have to create FloatBuffer view objects since most calls have a version that receives pure ByteBuffers.

 

EDIT: I misread, you might not be creating a new direct buffer each call. You're still creating a new view each call though, you can (and should) hold onto that reference too instead of re creating it all the time.

 

Also this line here:

 

matrix_buffer.asFloatBuffer().put(m).flip(); //Write to buffer and set its capacity

 

It might not be doing what you think its doing. asFloatBuffer returns a new FloatBuffer object that basically points to the same region of memory as the ByteBuffer (well, address + current position exactly). Thing is, its a whole different object, if you call 'flip' on that view, it wont do anything to the position/limit/etc of the original ByteBuffer. 'ByteBuffer#asFloatBuffer' javadoc explains it in detail.

Edited by TheChubu

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Now

  • Advertisement
  • Similar Content

    • By Balma Alparisi
      i got error 1282 in my code.
      sf::ContextSettings settings; settings.majorVersion = 4; settings.minorVersion = 5; settings.attributeFlags = settings.Core; sf::Window window; window.create(sf::VideoMode(1600, 900), "Texture Unit Rectangle", sf::Style::Close, settings); window.setActive(true); window.setVerticalSyncEnabled(true); glewInit(); GLuint shaderProgram = createShaderProgram("FX/Rectangle.vss", "FX/Rectangle.fss"); float vertex[] = { -0.5f,0.5f,0.0f, 0.0f,0.0f, -0.5f,-0.5f,0.0f, 0.0f,1.0f, 0.5f,0.5f,0.0f, 1.0f,0.0f, 0.5,-0.5f,0.0f, 1.0f,1.0f, }; GLuint indices[] = { 0,1,2, 1,2,3, }; GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); GLuint vbo; glGenBuffers(1, &vbo); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW); GLuint ebo; glGenBuffers(1, &ebo); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, false, sizeof(float) * 5, (void*)0); glEnableVertexAttribArray(0); glVertexAttribPointer(1, 2, GL_FLOAT, false, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glEnableVertexAttribArray(1); GLuint texture[2]; glGenTextures(2, texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageOne = new sf::Image; bool isImageOneLoaded = imageOne->loadFromFile("Texture/container.jpg"); if (isImageOneLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageOne->getSize().x, imageOne->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageOne->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageOne; glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageTwo = new sf::Image; bool isImageTwoLoaded = imageTwo->loadFromFile("Texture/awesomeface.png"); if (isImageTwoLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageTwo->getSize().x, imageTwo->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageTwo->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageTwo; glUniform1i(glGetUniformLocation(shaderProgram, "inTextureOne"), 0); glUniform1i(glGetUniformLocation(shaderProgram, "inTextureTwo"), 1); GLenum error = glGetError(); std::cout << error << std::endl; sf::Event event; bool isRunning = true; while (isRunning) { while (window.pollEvent(event)) { if (event.type == event.Closed) { isRunning = false; } } glClear(GL_COLOR_BUFFER_BIT); if (isImageOneLoaded && isImageTwoLoaded) { glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glUseProgram(shaderProgram); } glBindVertexArray(vao); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr); glBindVertexArray(0); window.display(); } glDeleteVertexArrays(1, &vao); glDeleteBuffers(1, &vbo); glDeleteBuffers(1, &ebo); glDeleteProgram(shaderProgram); glDeleteTextures(2,texture); return 0; } and this is the vertex shader
      #version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
      #version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

    • By khawk
      We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
      Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

      View full story
    • By TheChubu
      The Khronos™ Group, an open consortium of leading hardware and software companies, announces from the SIGGRAPH 2017 Conference the immediate public availability of the OpenGL® 4.6 specification. OpenGL 4.6 integrates the functionality of numerous ARB and EXT extensions created by Khronos members AMD, Intel, and NVIDIA into core, including the capability to ingest SPIR-V™ shaders.
      SPIR-V is a Khronos-defined standard intermediate language for parallel compute and graphics, which enables content creators to simplify their shader authoring and management pipelines while providing significant source shading language flexibility. OpenGL 4.6 adds support for ingesting SPIR-V shaders to the core specification, guaranteeing that SPIR-V shaders will be widely supported by OpenGL implementations.
      OpenGL 4.6 adds the functionality of these ARB extensions to OpenGL’s core specification:
      GL_ARB_gl_spirv and GL_ARB_spirv_extensions to standardize SPIR-V support for OpenGL GL_ARB_indirect_parameters and GL_ARB_shader_draw_parameters for reducing the CPU overhead associated with rendering batches of geometry GL_ARB_pipeline_statistics_query and GL_ARB_transform_feedback_overflow_querystandardize OpenGL support for features available in Direct3D GL_ARB_texture_filter_anisotropic (based on GL_EXT_texture_filter_anisotropic) brings previously IP encumbered functionality into OpenGL to improve the visual quality of textured scenes GL_ARB_polygon_offset_clamp (based on GL_EXT_polygon_offset_clamp) suppresses a common visual artifact known as a “light leak” associated with rendering shadows GL_ARB_shader_atomic_counter_ops and GL_ARB_shader_group_vote add shader intrinsics supported by all desktop vendors to improve functionality and performance GL_KHR_no_error reduces driver overhead by allowing the application to indicate that it expects error-free operation so errors need not be generated In addition to the above features being added to OpenGL 4.6, the following are being released as extensions:
      GL_KHR_parallel_shader_compile allows applications to launch multiple shader compile threads to improve shader compile throughput WGL_ARB_create_context_no_error and GXL_ARB_create_context_no_error allow no error contexts to be created with WGL or GLX that support the GL_KHR_no_error extension “I’m proud to announce OpenGL 4.6 as the most feature-rich version of OpenGL yet. We've brought together the most popular, widely-supported extensions into a new core specification to give OpenGL developers and end users an improved baseline feature set. This includes resolving previous intellectual property roadblocks to bringing anisotropic texture filtering and polygon offset clamping into the core specification to enable widespread implementation and usage,” said Piers Daniell, chair of the OpenGL Working Group at Khronos. “The OpenGL working group will continue to respond to market needs and work with GPU vendors to ensure OpenGL remains a viable and evolving graphics API for all its customers and users across many vital industries.“
      The OpenGL 4.6 specification can be found at https://khronos.org/registry/OpenGL/index_gl.php. The GLSL to SPIR-V compiler glslang has been updated with GLSL 4.60 support, and can be found at https://github.com/KhronosGroup/glslang.
      Sophisticated graphics applications will also benefit from a set of newly released extensions for both OpenGL and OpenGL ES to enable interoperability with Vulkan and Direct3D. These extensions are named:
      GL_EXT_memory_object GL_EXT_memory_object_fd GL_EXT_memory_object_win32 GL_EXT_semaphore GL_EXT_semaphore_fd GL_EXT_semaphore_win32 GL_EXT_win32_keyed_mutex They can be found at: https://khronos.org/registry/OpenGL/index_gl.php
      Industry Support for OpenGL 4.6
      “With OpenGL 4.6 our customers have an improved set of core features available on our full range of OpenGL 4.x capable GPUs. These features provide improved rendering quality, performance and functionality. As the graphics industry’s most popular API, we fully support OpenGL and will continue to work closely with the Khronos Group on the development of new OpenGL specifications and extensions for our customers. NVIDIA has released beta OpenGL 4.6 drivers today at https://developer.nvidia.com/opengl-driver so developers can use these new features right away,” said Bob Pette, vice president, Professional Graphics at NVIDIA.
      "OpenGL 4.6 will be the first OpenGL release where conformant open source implementations based on the Mesa project will be deliverable in a reasonable timeframe after release. The open sourcing of the OpenGL conformance test suite and ongoing work between Khronos and X.org will also allow for non-vendor led open source implementations to achieve conformance in the near future," said David Airlie, senior principal engineer at Red Hat, and developer on Mesa/X.org projects.

      View full story
    • By _OskaR
      Hi,
      I have an OpenGL application but without possibility to wite own shaders.
      I need to perform small VS modification - is possible to do it in an alternative way? Do we have apps or driver modifictions which will catch the shader sent to GPU and override it?
    • By xhcao
      Does sync be needed to read texture content after access texture image in compute shader?
      My simple code is as below,
      glUseProgram(program.get());
      glBindImageTexture(0, texture[0], 0, GL_FALSE, 3, GL_READ_ONLY, GL_R32UI);
      glBindImageTexture(1, texture[1], 0, GL_FALSE, 4, GL_WRITE_ONLY, GL_R32UI);
      glDispatchCompute(1, 1, 1);
      // Does sync be needed here?
      glUseProgram(0);
      glBindFramebuffer(GL_READ_FRAMEBUFFER, framebuffer);
      glFramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                     GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture[1], 0);
      glReadPixels(0, 0, kWidth, kHeight, GL_RED_INTEGER, GL_UNSIGNED_INT, outputValues);
       
      Compute shader is very simple, imageLoad content from texture[0], and imageStore content to texture[1]. Does need to sync after dispatchCompute?
  • Advertisement