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OpenGL Working with OGL3.x-

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Hi!
I've been setting up a new context for some time now. And I finally seem to get to grips with it. However, I can't render anything in my window, which is quite crippling...

I'm loading an OBJ into vectors and load that information into a couple of VBO's for texccords, vertex position, normals and a vector for indices.
I know for a fact that the code I'm using is functional under lower contexts and I just can't get it to work in the new one.

I'm thinking that it's got something to do with using my own matrices and how the shaders are set up... but I can't figure it out.

My render function:
void cOpenGLContext::renderScene(void) {
glViewport(0, 0, windowWidth, windowHeight); // set the viewport to fill the entire window
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); // clear required buffers

viewMatrix = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, 0.0f, -5.0f)); // create our view matrix which will translate us back 5 units
modelMatrix = glm::scale(glm::mat4(1.0f), glm::vec3(0.5f));// create our model matrix which will halve the size of our model

shader->bind();
int projectionMatrixLocation = glGetUniformLocation(shader->id(), "projectionMatrix"); // get the location of our projection matrix in the shader
int viewMatrixLocation = glGetUniformLocation(shader->id(), "viewMatrix"); // get the location of our view matrix in the shader
int modelMatrixLocation = glGetUniformLocation(shader->id(), "modelMatrix"); // get the location of our model matrix in the shader

glUniformMatrix4fv(projectionMatrixLocation, 1, GL_FALSE, &projectionMatrix[0][0]);// send our projection matrix to the shader
glUniformMatrix4fv(viewMatrixLocation, 1, GL_FALSE, &viewMatrix[0][0]); // send our view matrix to the shader
glUniformMatrix4fv(modelMatrixLocation, 1, GL_FALSE, &modelMatrix[0][0]); // send our model matrix to the shader

// rest of render function here
// VBO [start]
// drawing
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
// vertex buffer
glBindBuffer(GL_ARRAY_BUFFER, earth.vBufferObject);
glVertexPointer(3, GL_FLOAT, 0, 0);

// texture buffer
glBindBuffer(GL_ARRAY_BUFFER, earth.tBufferObject);
glTexCoordPointer(3, GL_FLOAT, 0, 0);

// normal buffer
glBindBuffer(GL_ARRAY_BUFFER, earth.nBufferObject);
glNormalPointer(GL_FLOAT, 0, 0);

// index buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, earth.iBufferObject);

// draws it all
glDrawElements(GL_TRIANGLES, earth.vFaces.size(), GL_UNSIGNED_INT, 0);

// unbinds the buffers
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisableClientState(GL_NORMAL_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
// drawing end
shader->unbind();

SwapBuffers(hdc); // swap buffers so we can see our rendering
}





My shaders

// vert
#version 150 core

in vec3 in_Position;
in vec3 in_Color;
out vec3 pass_Color;

uniform mat4 projectionMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;

void main(void) {
gl_Position = projectionMatrix * viewMatrix * modelMatrix * vec4(in_Position, 1.0);
pass_Color = in_Color;
}



// frag
#version 150 core

in vec3 pass_Color;
out vec4 out_Color;

void main(void) {
out_Color = vec4(pass_Color, 1.0);
}





Can anyone see what I'm doing wrong? I'm going blind, staring at this code.

Thanks!
Marcus

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It looks like you need to study the 3.x specification a bit more closely. OpenGL 3 deprecates a lot of functionality. Just skimming over your code, I can see lots of deprecated code: glEnableClientState, glVertexPointer, etc. You need to learn how to use vertex attribute arrays.

If you are running OpenGL 3.2 or later, those functions simply will not work at all. Running 3.1 should enable that deprecated functionality.

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Hi, TheBuzzSaw.
Do you mean something like:

// function for setting up the buffers
glGenBuffers(1, &vBufferObject);
glBindBuffer(GL_ARRAY_BUFFER, vBufferObject);
glBufferData(GL_ARRAY_BUFFER, ((int)(vertices.size()) * 3 * sizeof(float)), &(vertices.at(0)), GL_STATIC_DRAW);
glVertexAttribPointer((GLuint)0, 3, GL_FLOAT, GL_FALSE, 0, 0);

// ...

// draw function
glBindVertexArray(earth.vBufferObject);
glDrawArrays(GL_TRIANGLES, 0, 3);


Thanks for your previous answer.

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Quote:
Original post by Trefall
Here's how I use VAO and VBO: Cube.cpp


Thanks for posting that. That's how I'm doing it right now. But I'm still not getting anything on the screen. Just my regular background.

// vao, vbo, ibo setup
vao = 0;

// vertex buffer
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

glGenBuffers(1, &vBufferObject);
glBindBuffer(GL_ARRAY_BUFFER, vBufferObject);
glBufferData(GL_ARRAY_BUFFER, sizeof(float)*vertices.size(), NULL, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float)*vertices.size(), &vertices[0]);


//.....


// render function
glBindVertexArray(earth.vao);
glDrawElements(GL_TRIANGLES, earth.vFaces.size(), GL_UNSIGNED_INT, 0);
glBindVertexArray(0);


Thanks for the help, guys.

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I assume you also bind and buffer your index list? :) Use this snippet to see if OpenGL is throwing any errors internally:


{
GLenum err = glGetError();
if(err != GL_NO_ERROR)
std::cout << "OpenGL prog error: " << gluErrorString(err) << std::endl;
std::cout.flush();
}

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You also may want to calculate your modelview * projection matrix on the CPU and uploading it once to the GPU instead of doing it per-vertex. The model matrix has to be passed up separately for each unique object. The only access you have to the GL default attributes is to the gl_* attributes in your shader. User defined attributes have to be bound and specified by the user...it doesn't happen automagically. See the GLSL spec for reference. With that said your shader is transforming some unknown attributes since the default vertex attribute that is bound to glVertexPointer is gl_Vertex which is not valid when version 150 is define.

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Quote:
Original post by cgrant
You also may want to calculate your modelview * projection matrix on the CPU and uploading it once to the GPU instead of doing it per-vertex. The model matrix has to be passed up separately for each unique object. The only access you have to the GL default attributes is to the gl_* attributes in your shader. User defined attributes have to be bound and specified by the user...it doesn't happen automagically. See the GLSL spec for reference. With that said your shader is transforming some unknown attributes since the default vertex attribute that is bound to glVertexPointer is gl_Vertex which is not valid when version 150 is define.


Allright, seems like I've got quite a bit to rework, then.
- Calculate modelview * projection matrix on the CPU and upload it to the GPU once for each unique object
- Since I'm using GLSL version 150 I need some other way to point to my vertices.

Taking another look at the GLSL and OpenGL specifications.

Thanks!

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Quote:
Original post by TheBuzzSaw
You don't wanna be using GLU in OpenGL 3.


You should correct that comment to: "you don't want to use GLU functionality that use deprecated OpenGL functionality" ;) gluErrorString is perfectly safe to use with OpenGL 3.x, and is quite convenient actually. Of course, you could always make your own string registry on GL error enums.

Quote:
Original post by tre
- Since I'm using GLSL version 150 I need some other way to point to my vertices.


Just send them in as attributes, with a buffer offset towards your VBO. Since you only have vertices in the vbo, that means you will point to the first element of your vbo. OpenGL will handle the rest for you :) If you refer back to my Cube.cpp you'll see how I've handled this.


#ifndef BUFFER_OFFSET
#define BUFFER_OFFSET(bytes) ((GLubyte*) NULL + bytes)
#endif

static void shaderAttrib(unsigned int prog, const char *attribName, int size, GLenum type, bool normalized, int stride, void* pointer)
{
int id = glGetAttribLocation(prog, attribName);
if(id < 0)
throw CL_Exception(cl_format("Failed to load attribute %1", attribName));

glVertexAttribPointer(id, size, type, normalized, stride, pointer);
glEnableVertexAttribArray(id);
}

//usage:
shaderAttrib(shader.getShaderProg(), "vVertex", 3, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));



Just make sure you use it while the VAO/VBO is still bound.

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Quote:
Original post by tre
Allright, seems like I've got quite a bit to rework, then.
- Calculate modelview * projection matrix on the CPU and upload it to the GPU once for each unique object
- Since I'm using GLSL version 150 I need some other way to point to my vertices.

Taking another look at the GLSL and OpenGL specifications.

Thanks!


Don't be afraid to transmit several matrices into the shaders either. For instance, some shader designs require access to just the model view or just the projection. However, you still don't want every single vertex doing unnecessary matrix math, so it is still smart to transmit the pre-multiplied model view projection matrix. One of my shaders, for instance, has uniform matrices "MVPM", "MVM", and "PM".

Quote:
Original post by Trefall
You should correct that comment to: "you don't want to use GLU functionality that use deprecated OpenGL functionality" ;) gluErrorString is perfectly safe to use with OpenGL 3.x, and is quite convenient actually. Of course, you could always make your own string registry on GL error enums.


Fair enough. The only stuff I was using from GLU back in the day was gluPerspective and gluUnProject. I just looked up how they were both calculated and rid myself my GLU entirely. It's also an annoying extra dependency in projects. XD

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Allright. After some time I've got my program up and running with drawing happening.
The problem I'm facing now is that my model is not being drawn correctly. I've had this problem before and I think I know the cause - reading in an OBJ-file and only drawing the vertices messes it up when trying to draw anything else than GL_POINTS.
However, I don't know of any way to draw using face indices instead of the raw vertex data, using VAO's and VBO's.

The way I'm setting up my VAO+VBO:
// vertex buffer
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

glGenBuffers(1, &vBufferObject);
glBindBuffer(GL_ARRAY_BUFFER, vBufferObject);
glBufferData(GL_ARRAY_BUFFER, sizeof(float)*vertices.size(), NULL, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float)*vertices.size(), &vertices[0]);



So, that's setting up my VAO+VBO using a vertex array. I'll have to change this so that the program reads and loads the indices. How?

Then the rendering part:
...
glBindVertexArray(vaoID[0]);
glDrawArrays(GL_TRIANGLE_STRIP, 0, earth.vertices.size());
glBindVertexArray(0);
...



How does this have to change to draw the model using the face indices? I just can't seem to find any good information on drawing using those instead. Maybe I'm stupid, but I just can't.

If anyone would like to explain it to me or point me in the right direction, it'd be great.

Thanks again, guys!
Marcus

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Quote:
Original post by TheBuzzSaw
If you are trying to draw OBJ data, where are your indices? Look into using glDrawElements.


My indices are loaded when the model is loaded and set up last of the buffers for vertices, texture coordinates and normals.

Here:
// index buffer
glGenBuffers(1, &iBufferObject);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iBufferObject);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, ((int)(vFaces.size()) * 3 * sizeof(float)), &(vFaces.at(0)), GL_STATIC_DRAW);


I were looking at glDrawElements... at the moment I'm loading all my vertex information from a Vertex Array Object. How is the process when using the indices? The same? As I understand it a VBO can be loaded with any information (vertex, normal, elements, texture coordinates) and a VAO can be loaded with several VBO's.

I don't know if you can tell, but I'm a little confused about how to go about this :)

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VBOs hold any sort of data in OpenGL, VAOs hold OpenGL state that should be applied for a single rendering call.

VAOs are there just for convenience, so you wont need to bind your buffers and make the pointers every single time you want to draw with your buffers.

Now, you can have as many (or there's probably a limit you will never get to) VBOs holding vertex data (GL_ARRAY_BUFFER) in a VAO, and one indices VBO (GL_ELEMENT_ARRAY_BUFFER).
If the VAO has an indices buffer, you can then use any rendering functions that use indices, glDraw*Elements*.

Here's a very good site teaching OpenGL 3.3 http://www.arcsynthesis.org/gltut/index.html

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      Creating the Pipeline State Object
      After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
      PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
      Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
      // Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
      // Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
      Binding Shader Resources
      Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
      Static variables (SHADER_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. Mutable variables (SHADER_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc. Dynamic variables (SHADER_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
      Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
      PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new Shader Resource Binding object (SRB) that is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):
      m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
      Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
      m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
      m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
      As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
      This post gives more details about the resource binding model in Diligent Engine.
      Setting the Pipeline State and Committing Shader Resources
      Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
      m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
      DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
      AntTweakBar sample is Diligent Engine’s “Hello World” example.

       
      Atmospheric scattering sample is a more advanced example. It demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
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