I have two variables that I'm getting from shader in opengl. I do something like this.
vLoc = glGetAttribLocation(progId,"vPosition");
nLoc = glGetAttribLocation(progId,"vNormal");
matViewLoc = glGetUniformLocation(progId,"matView");
matProjLoc = glGetUniformLocation(progId,"matProj");
matTranslateLoc = glGetUniformLocation(progId,"matTranslate");
vLoc and projLoc return the same location. Would anybody know why? Thanks!
The space for uniform locations and attribute locations is different, so you can have same IDs, but they refer to different objects.
You can't pass a attribute location to a glUniform function or a uniform location to a attrib function.
did you bind the attrib location when you created the shader program using glBindAttribLocation?
You need something like this:
glBindAttribLocation(progId, 0, "vPosition");
glBindAttribLocation(progId, 1, "vNormal");
Related
I want to transform data from geometry shaders to feedback buffer,so I set the names of variables like this:
char *Varying[] = {"lColor","lPos","gl_NextBuffer","rColor","rPos"};
then bind two buffers vbos[2] to transformFeedback object Tfb,vbos[0] to bind point 0, and vbos[1] to bind point 2:
glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, vbos[0]);
glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 2, vbos[1]);
and set stream number like this:
layout(stream=0) out vec4 lColor;
layout(stream=0) out vec4 lPos;
layout(stream = 2) out rVert
{
vec4 rColor;
vec4 rPos;
};
So I thought lColor and lPos are transformed to vbos[0],rColor and rPos are transformed to vbos[1],but nothing came out,unless I change vbos[1] to bind point 1,and stream number of rvert to 1.
I think there is three variables about indexes for binding geometry shader output and feedback buffers,first is index in glBindBufferBase(target,index,id),second is sequences of names in glTransformFeedbackVaryings(program,count,names,buffermode),third is stream number of variables in geometry shader,what is the relationship of these three parameters?
And I found that no matter what parameters I set the glDrawTransformFeedbackStream ,picture didn't change,Why?
The geometry shader layout qualifier stream has no direct relationship to the TF buffer binding index assignment. There is one caveat here: variables from two different streams can't be assigned to the same buffer binding index. But aside from that, the two have no relationship.
In geometry shader transform feedback, streams are written independently of each other. When you output a vertex/primitive, you say which stream the GS invocation is writing. Only the output variables assigned to that stream are written, and the system keeps track of how much stuff has been written to each stream.
But how the output variables map to feedback buffers is entirely separate (aside from the aforementioned caveat).
In your example, glTransformFeedbackVaryings with {"lColor","lPos","gl_NextBuffer","rColor","rPos"} does the following. It starts with buffer index 0. It assigns lColor and lPos to buffer index 0. gl_NextBuffer causes the system to increment the value of the current buffer index. That value is 0, so incrementing it makes it 1. It then assigns rColor and rPos to buffer 1.
That's why your code doesn't work.
You can skip buffer indices in the TF buffer bindings. To do that, you have to use gl_NextBuffer twice, since each use increments the current buffer index.
Or if your GL version is high enough, you can just assign the buffer bindings and offsets directly in your shader:
layout(stream=0, xfb_offset = 0, xfb_buffer = 0) out vec4 lColor;
layout(stream=0, xfb_offset = 16, xfb_buffer = 0) out vec4 lPos;
layout(stream = 2, xfb_offset = 0, xfb_buffer = 2) out rVert
{
vec4 rColor;
vec4 rPos;
};
I'm trying to make a simple compute shader using a Shader Storage Buffer (SSBO) to pass data to the shader. I'm coding in C++ with GLFW3 and GLEW. I'm passing an array of integers into an SSBO, binding it to the index 0, and expecting to retrieve the data in the shader from a layout buffer variable (as explained on various websites). However, I get an unexpected "undefined variable" error on shader compilation concerning this layout buffer variable, though it is clearly declared.
Here is the GLSL code of the compute shader (this script is only at its beginning) :
#version 430
layout (local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
layout (std430, binding = 0) buffer params
{
ivec3 dims;
};
int index(ivec3 coords){
ivec3 dims = params.dims;
return coords.x + dims.y * coords.y + dims.x * dims.y * coords.z;
}
void main() {
ivec3 coords = ivec3(gl_GlobalInvocationID);
int i = index(coords);
}
I get the error : 0(12) : error C1503: undefined variable "params"
Here is the C++ script that setups and runs the compute shader :
int dimensions[] {width, height, depth};
GLuint paramSSBO;
glGenBuffers(1, ¶mSSBO);
glBindBuffer(GL_SHADER_STORAGE_BUFFER, paramSSBO);
glBufferData(GL_SHADER_STORAGE_BUFFER, sizeof(dimensions), &dimensions, GL_STREAM_READ);
glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, paramSSBO);
glBindBuffer(GL_SHADER_STORAGE_BUFFER, 0);
GLuint computeShaderID;
GLuint csProgramID;
char* computeSource;
loadShaderSource(computeSource, "compute.glsl");
computeShaderID = glCreateShader(GL_COMPUTE_SHADER);
compileShader(computeShaderID, computeSource);
delete[] computeSource;
csProgramID = glCreateProgram();
glAttachShader(csProgramID, computeShaderID);
glLinkProgram(csProgramID);
glDeleteShader(computeShaderID);
glUseProgram(csProgramID);
glDispatchCompute(width, height, depth);
glMemoryBarrier(GL_BUFFER_UPDATE_BARRIER_BIT);
glUseProgram(0);
glDeleteBuffers(1, ¶mSSBO);
width, height and depth are int variables defined earlier in the program. I'm binding the dimensions array to the index 0 and I expect to retrieve it in the ivec3 params.dims variable in the shader. However the params variable is said to be undefined when used in the index() function.
This script is just the beginning and I wanted to add a second buffer where the shader would actually write its result, but I'm stuck here. For clarification : in the complete script I expect not to write in any texture (as all online examples show), but write the results in the second buffer from which I will get the data back into a C++ array for further use.
params is not a variable. Nor is it a struct or class. It is the name of an interface block. And the name of an interface block is not really part of GLSL itself; it's part of OpenGL. It's the name used by the OpenGL API to represent that particular block.
You never use an interface block's name in the shader text itself, outside of defining it.
Unless you give your interface block an instance name, the names of all variables within that block are essentially part of the global namespace. Indeed, scoping those names is the whole point of giving the block an instance name.
So the correct way to access the dims field in the interfae block is as "dims".
I need to index into array of 2 uniform sampler2D. The index is dynamic per frame.That's,I have a dynamic uniform buffer which provides that index to a fragment shader. I use Vulkan API 1.2. In device feature listing I have:
shaderSampledImageArrayDynamicIndexing = 1
I am not sure 100% but It looks like this feature is core in 1.2.Nevertheless I did try to enable it during device creation like this:
VkPhysicalDeviceFeatures features = {};
features.shaderSampledImageArrayDynamicIndexing = VK_TRUE;
Then plugging into device creation:
VkDeviceCreateInfo deviceCreateInfo = {};
deviceCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
deviceCreateInfo.pQueueCreateInfos = queueCreateInfos;
deviceCreateInfo.queueCreateInfoCount = 1;
deviceCreateInfo.pEnabledFeatures = &features ;
deviceCreateInfo.enabledExtensionCount = NUM_DEVICE_EXTENSIONS;
deviceCreateInfo.ppEnabledExtensionNames = deviceExtensionNames;
In the shader it looks like this:
layout(std140,set=0,binding=1)uniform Material
{
vec4 fparams0;
vec4 fparams1;
uvec4 iparams; //.z - array texture idx
uvec4 iparams1;
}material;
layout (set=1,binding = 0)uniform sampler2D u_ColorMaps[2];
layout (location = 0)in vec2 texCoord;
layout(location = 0) out vec4 outColor;
void main()
{
outColor = texture(u_ColorMaps[material.iparams.z],texCoord);
}
What I get is a combination of image pixels with some weird color. If I change to fixed indices - it works correctly. material.iparams.z param has been verified,it provides correct index number every frame (0 or 1). No idea what else is missing.Validation layers say nothing.
Mys setup: Windows, RTX3000 ,NVIDIA beta driver 443.41 (Vulkan 1.2)
Update:
I also found that dynamically indexed sampler return a value in Red channel (r)
which is close to one and zeros in GB. I don't set red color anyway,also the textures I fetch don't contain red. Here are two sreenshot, the upper is correct result which I get when indexing with constant value. Second is what happens when I index with dynamic uint which comes from dynamic UBO:
Correct
Wrong
The problem was due to usage of Y′CBCR samplers. It appears that Vulkan disallows indexing dynamically into array of such uniforms.
Here is what Vulkan specs says:
If the combined image sampler enables sampler Y′CBCR conversion or
samples a subsampled image, it must be indexed only by constant
integral expressions when aggregated into arrays in shader code,
irrespective of the shaderSampledImageArrayDynamicIndexing feature.
So,the solution for me was to provide two separately bound samplers and use dynamic indices with if()..else condition to decide which sampler to use. Push constants would also work,but in this case I have to re-record command buffers all the time. Hopefully this info will be helpful to other people working with video formats in Vulkan API.
I have a vertex shader:
#version 430
in vec4 position;
void main(void)
{
//gl_Position = position; => works in ALL cases
gl_Position = vec4(0,0,0,1);
}
if I do:
m_program.setAttributeArray(0, m_vertices.constData());
m_program.enableAttributeArray(0);
everything works fine. However, if I do:
m_program.setAttributeArray("position", m_vertices.constData());
m_program.enableAttributeArray("position");
NOTE: m_program.attributeLocation("position"); returns -1.
then, I get an empty window.
Qt help pages state:
void QGLShaderProgram::setAttributeArray(int location, const QVector3D
* values, int stride = 0)
Sets an array of 3D vertex values on the attribute at location in this shader program. The stride indicates the
number of bytes between vertices. A default stride value of zero
indicates that the vertices are densely packed in values.
The array will become active when enableAttributeArray() is called on
the location. Otherwise the value specified with setAttributeValue()
for location will be used.
and
void QGLShaderProgram::setAttributeArray(const char * name, const
QVector3D * values, int stride = 0)
This is an overloaded function.
Sets an array of 3D vertex values on the attribute called name in this
shader program. The stride indicates the number of bytes between
vertices. A default stride value of zero indicates that the vertices
are densely packed in values.
The array will become active when enableAttributeArray() is called on
name. Otherwise the value specified with setAttributeValue() for name
will be used.
So why is it working when using the "int version" and not when using the "const char * version"?
It returns -1 because you commented out the only line in your shader that actually uses position.
This is not an error, it is a consequence of a misunderstanding how attribute locations are assigned. Uniforms and attributes are only assigned locations after all shader stages are compiled and linked. If a uniform or attribute is not used in an active code path it will not be assigned a location. Even if you use the variable to do something like this:
#version 130
in vec4 dead_pos; // Location: N/A
in vec4 live_pos; // Location: Probably 0
void main (void)
{
vec4 not_used = dead_pos; // Not used for vertex shader output, so this is dead.
gl_Position = live_pos;
}
It actually goes even farther than this. If something is output from a vertex shader but not used in a geometry, tessellation or fragment shader, then its code path is considered inactive.
Vertex attribute location 0 is implicitly vertex position, by the way. It is the only vertex attribute that the GLSL spec. allows to alias to a fixed-function pointer function (e.g. glVertexPointer (...) == glVertexAttribPointer (0, ...))
I'm currently trying to draw simple meshes using different textures (using C# and OpenTK). I read a lot about TextureUnit and bindings, and that's my current implementation (not working as expected) :
private void ApplyOpaquePass()
{
GL.UseProgram(this.shaderProgram);
GL.CullFace(CullFaceMode.Back);
while (this.opaqueNodes.Count > 0)
Draw(this.opaqueNodes.Pop());
GL.UseProgram(0);
}
And my draw method :
private void Draw(Assets.Model.Geoset geoset)
{
GL.ActiveTexture(TextureUnit.Texture1);
GL.BindTexture(TextureTarget.Texture2D, geoset.TextureId /*buffer id returned by GL.GenTextures*/ );
GL.Uniform1(GL.GetUniformLocation(this.shaderProgram, "Texture1"), 1 /*see note below*/ );
//Note: if I'm correct, it should be 1 when using TextureUnit.Texture1
// (2 for Texture2...), note that doesn't seem to work since no
// texture texture at all is sent to the shader, however a texture
// is shown when specifying any other number (0, 2, 3...)
// Draw vertices & indices buffers...
}
And my shader code (that shouldn't be the problem since uv mapping is ok):
uniform sampler2D Texture1;
void main(void)
{
gl_FragColor = texture2D(Texture1, gl_TexCoord[0].st);
}
What's the problem :
Since geoset.TextureId can vary from one geoset to another, I'm expecting different texture to be sent to the shader.
Instead, always the same texture is applied to all objects (geosets).
Ideas :
Using different TextureUnit for each textures (working well), but what happens if we have 2000 different textures? If my understanding is right, we must use multiple TextureUnit only if we want to use multiple texture at the same time in the shader.
I first thought that uniforms couldn't be changed once defined, but a test with a boolean uniform told me that it was actually possible.
private void Draw(Assets.Model.Geoset geoset)
{
GL.ActiveTexture(TextureUnit.Texture1);
GL.BindTexture(TextureTarget.Texture2D, geoset.TextureId);
GL.Uniform1(GL.GetUniformLocation(this.shaderProgram, "Texture1"), 1 );
//added line...
GL.Uniform1(GL.GetUniformLocation(this.shaderProgram, "UseBaseColor"), (geoset.Material.FilterMode == Assets.Model.Material.FilterType.Blend) ? 1: 0);
// Draw vertices & indices buffers...
}
Shader code:
uniform sampler2D Texture1;
uniform bool UseBaseColor;
void main(void)
{
gl_FragColor = texture2D(Texture1, gl_TexCoord[0].st);
if (UseBaseColor)
gl_FragColor = mix(vec4(0,1,1,1), gl_FragColor , gl_FragColor .a);
}
This code works great, drawing some geoset with a base color instead of transparency, that (should ?) prove that uniforms can be changed here. Why this isn't working with my textures ?
Should I use a different shader program per geoset ?
Thanks in advance for your answers :)
Regards,
Bruce
EDIT: that's how I generate textures in the renderer:
override public uint GenTexture(Bitmap bmp)
{
uint texture;
GL.GenTextures(1, out texture);
//I disabled this line because I now bind the texture before drawing a geoset
//Anyway, uncommenting this line doesn't show a better result
//GL.BindTexture(TextureTarget.Texture2D, texture);
System.Drawing.Imaging.BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, data.Width, data.Height, 0,
OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, data.Scan0);
bmp.UnlockBits(data);
//temp settings
GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Linear);
GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear);
return texture;
}
I finally solved my problem !
All the answers perfected my understanding and lead me to the solution which lied on two major problems:
1) as Calvin1602 said, this is very important to bind a newly created texture before calling glTexImage2d.
2) also UncleZeiv rose my attention about the last GL.Uniform1's parameter. The OpenTK tutorial is very misleading because the guy pass the id of the texture object to the function, that happens to work here because the order of generation of the texture exactly matches the id of used TextureUnit.
As I was unsure that my comprehension was exact, I wrongly changed this parameter back to the geoset.TextureId.
Thanks !
You don't need multiple shader programs if the only thing you are changing is the texture. Also uniform locations are constant throughout the lifetime of a shader program, so there is no need to retrieve those each frame. However, you do need to rebind the texture each time you change it, and you will need to bind each distinct texture to a separate texture ID.
As a result, I would conclude that what you posted ought to work and so the problem is likely somewhere else in your code.
EDIT: After the updated version it should still work. However I am concerned about why the following line is commented out:
//GL.BindTexture(TextureTarget.Texture2D, texture);
This should be in there. Otherwise you will keep over writing the same texture (which is ridiculous). You need to bind the texture before you initialize. Now it is entirely conceivable that something else is broken, but given what I see now this is the only error that jumps out at me.