Hello Guest

Get the size of uniforms

  • 5 Replies
  • 458 Views
Get the size of uniforms
« on: August 05, 2018, 16:24:12 »
Hello,

I'm trying to set up UBOs in my application but I'm not able to get the uniform' sizes in my uniform block.
Here is the code I use to get the size :

Code: [Select]
private void setUpUniformsOffsetsAndSizes(UniformBufferObjectInfos uniformBufferObjectInfos) {

int shaderProgramID = uniformBufferObjectInfos.getShaderProgramID();
String[] uniformNames = uniformBufferObjectInfos.getUniformsNames();
int nbUniforms = uniformNames.length;

// Retrieve the index of each uniform
IntBuffer uniformIndices = BufferUtils.createIntBuffer(nbUniforms);
GL31.glGetUniformIndices(shaderProgramID, uniformNames, uniformIndices);

// Retrieve the offset of each uniform
IntBuffer uniformsOffsets = BufferUtils.createIntBuffer(nbUniforms);
GL31.glGetActiveUniformsiv(shaderProgramID, uniformIndices, GL31.GL_UNIFORM_OFFSET, uniformsOffsets);

// Retrieve the size of each uniform
IntBuffer uniformsSizes = BufferUtils.createIntBuffer(nbUniforms);
GL31.glGetActiveUniformsiv(shaderProgramID, uniformIndices, GL31.GL_UNIFORM_SIZE, uniformsSizes);


// Store offset and size in UniformBufferObjectInfos
uniformBufferObjectInfos.setUniformsOffsets(uniformsOffsets);
uniformBufferObjectInfos.setUniformsSizes(uniformsSizes);

}

But I always get 1 when I'm asking for the sizes... My shader code is like this (I need the offset even if i'm using std140 here) :

Code: [Select]
layout (std140, binding = 0) uniform BlobSettings {
                        // Base Offset  // Base Alignment   // Aligned Offset
    vec4 innerColor;    // 0            // 16               // 0 - 15
    vec4 outerColor;    // 16           // 16               // 16 - 31
    float radiusInner;  // 32           // 4                // 32 - 35
    float radiusOuter;  // 36           // 4                // 36 - 40
};

Am I doing wrong ?

And finally, why does the BufferUtils class prevent us from doing like :

Code: [Select]
ByteBuffer updatedData = BufferUtils.createByteBuffer(4));
// do some stuff
bytes[] array = updatedData.array();

Because at some point in my code I need to convert my ByteBuffer to an array of bytes so the only solution I found was not to use BufferUtils :

Code: [Select]
ByteBuffer byteBuffer = ByteBuffer.allocate(values.length * 4).order(ByteOrder.nativeOrder());
for(float value : values) {
byteBuffer.putFloat(value);
}
byte[] bytesValues = byteBuffer.array();


Thanks for your help  :D
« Last Edit: August 05, 2018, 16:30:40 by xenoliss »

*

Offline KaiHH

  • ***
  • 150
Re: Get the size of uniforms
« Reply #1 on: August 05, 2018, 17:31:49 »
Read:
- http://www.lighthouse3d.com/tutorials/glsl-tutorial/uniform-blocks/
- https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGetActiveUniformBlock.xhtml

You should really first google a few tutorials about Uniform Blocks. Just google "OpenGL Uniform Blocks" and read the first few results.

Re: Get the size of uniforms
« Reply #2 on: August 05, 2018, 17:41:52 »
Thanks for your help KAIHH.

I already read this tutorials and this one : https://learnopengl.com/Advanced-OpenGL/Advanced-GLSL , as well as the one in "OpenGL programming Guide (OpenGL version 4.5)" and the one in "OpenGL 4 shading Language CookBook" and I think I understood the basics of uniforms blocks in GLSL but still I can't get the size of each uniform in my uniform block... I'm missing something  :-\

*

Offline KaiHH

  • ***
  • 150
Re: Get the size of uniforms
« Reply #3 on: August 05, 2018, 17:43:43 »
Then please read and follow that lighthouse3d tutorial again, and make sure you follow it exactly to the point. You are missing the GL call I mentioned in the other link. Please see the section "Setting and Updating the Buffer".

Re: Get the size of uniforms
« Reply #4 on: August 05, 2018, 17:50:24 »
I'm going to read it again. Thank you  :)

Re: Get the size of uniforms
« Reply #5 on: August 06, 2018, 12:05:48 »
Ok so I read it again and still can't get it to work... My code is the same as before and is the same as in the tutorial :

Java code  :

Code: [Select]
// Retrieve the uniform block index
int uniformBlockIndex = GL31.glGetUniformBlockIndex(shaderProgramID, uniformBlockName);

// Retrieve the binding point specified in the shader of the uniform block
int bindingPoint = GL31.glGetActiveUniformBlocki(shaderProgramID, uniformBlockIndex, GL31.GL_UNIFORM_BLOCK_BINDING);

// Retrieve the size of the uniform block
int sizeToAllocate = GL31.glGetActiveUniformBlocki(shaderProgramID, uniformBlockIndex, GL31.GL_UNIFORM_BLOCK_DATA_SIZE);

// Retrieve the number of active uniforms in the uniform block
int nbUniforms = GL31.glGetActiveUniformBlocki(shaderProgramID, uniformBlockIndex, GL31.GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS);

// Prepare a uniform buffer, allocating memory
int uboID = GL15.glGenBuffers();
GL15.glBindBuffer(GL31.GL_UNIFORM_BUFFER, uboID);
GL15.glBufferData(GL31.GL_UNIFORM_BUFFER, sizeToAllocate, GL15.GL_DYNAMIC_DRAW);

/*
 * Finaly bind the uniform buffer object to the same binding point to acctualy link
 * the uniform buffer to the uniform block (pointing each to the same binding point)
 */
GL30.glBindBufferBase(GL31.GL_UNIFORM_BUFFER, bindingPoint, uboID);
GL15.glBindBuffer(GL31.GL_UNIFORM_BUFFER, 0);

// Retrieve the index of each uniforms
IntBuffer uniformIndices = BufferUtils.createIntBuffer(nbUniforms);
GL31.glGetActiveUniformBlockiv(shaderProgramID, uniformBlockIndex, GL31.GL_UNIFORM_BLOCK_ACTIVE_UNIFORM_INDICES , uniformIndices);

// Retrieve the offset of each uniforms
IntBuffer uniformsOffsets = BufferUtils.createIntBuffer(nbUniforms);
GL31.glGetActiveUniformsiv(shaderProgramID, uniformIndices, GL31.GL_UNIFORM_OFFSET, uniformsOffsets);

// Retrieve the size of each uniforms  DOEST WORK fill the InteBuffer with Ones
IntBuffer uniformsSizes = BufferUtils.createIntBuffer(nbUniforms);
GL31.glGetActiveUniformsiv(shaderProgramID, uniformIndices, GL31.GL_UNIFORM_SIZE, uniformsSizes);

Shader code :

Code: [Select]
#version 460 core

in vec3 texCoords;

layout (location = 1) out vec4 fragColor;

layout (std140, binding = 0) uniform BlobSettings {
                        // Base Offset  // Base Alignment   // Aligned Offset
    vec4 innerColor;    // 0            // 16               // 0 - 15
    vec4 outerColor;    // 16           // 16               // 16 - 31
    float radiusInner;  // 32           // 4                // 32 - 35
    float radiusOuter;  // 36           // 4                // 36 - 40
};

void main(void) {

    float dx = texCoords.x - 0.5;
    float dy = texCoords.y - 0.5;
    float dist = sqrt(dx * dx + dy * dy);

    fragColor = mix(innerColor, outerColor, smoothstep(radiusInner, radiusOuter, dist));
}

Wich GL call am I missing  ???  ?
Thanks for your help.