OpenGL Bottom Row of 4x4 Matrix

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I'm writing a matrix library.

In an opengl matrix, you have:

R R R T
R R R T
R R R T
A A A B

where R is rotation and T is translation.

what is A and B?

how would I apply A and B to a Vec3? ( I know how to translate and rotate )

how would I invert A and B?

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well first take a look at this:
http://www.songho.ca/opengl/gl_transform.html
(the other pages are very useful too!!! so look around)

I'm not really sure if A is used at all, I did this a long time ago, but B is supposed to be the perspective divide element.
Or at least B and the projection matrix modify the 4th element of the position, so that in clip space if you divide by it, you get the ndc coordinates.
like when you do the transformations:
-Model (world) space (apply T here):
model_space_pos = model_mat * vertex
-View (camera) space (apply R here):
view_space_pos = view_mat * model_space_pos
-Clip space (apply projection matrix here):
clip_space_pos = projection_mat * view_space_pos
-normalized device coordinates (do the perspective divide, apply B here):
ndc_pos = clip_space_pos.xyz / clip_space_pos.w
-viewport coordinates (scale & bias to get texture coordinates, scale by window coordinates)
viewport_pos = (ndc_pos.xy * 0.5 + 0.5) * vec2( screen_width, screen_height )

and to the other questions:
you would apply the 4x4 matrix to a 4 component vector (ie vec4)
and you would invert A and B by inverting the 4x4 matrix.

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I'm not really sure if A is used at all, I did this a long time ago, but B is supposed to be the perspective divide element.
Or at least B and the projection matrix modify the 4th element of the position, so that in clip space if you divide by it, you get the ndc coordinates.

The entire bottom row is used for the perspective division, not just the B-element.

For example, for an orthographic projection, the bottom row is [0, 0, 0, x] where x is some value depending on the parameters of the projection matrix. That means that the fourth component of the resulting vector after multiplication is the fourth component of the in multiplying vector, to some scale factor. For glOrtho, x=1 at all times though, which means that as long as the Z-coordinate of the input is 1.0, which is often the case, there fourth component of the resulting vector is also 1.0, and there is effectively no perspective division, hence no perspective since it is an orthographic projection.

On the other hand, for a perspective matrix, the bottom row is [0, 0, x, 0]. That means that the fourth component of the resulting vector is the third component of the multiplying vector, to some scale factor x. The third component is the depth, and hence the perspective division is now dependent on the depth; you now get a perspective effect.

Likewise, the first two elements of the bottom row can also be non-zero to get a perspective effect along the X and/or the Y-axis instead.

how would I apply A and B to a Vec3? ( I know how to translate and rotate )

It doesn't make much sense to talk about how to apply these elements to a 3-element vector. You simply cannot multiply a 3-element vector by a 4-by-4 matrix in the first place. What you do when adding multiplying the 3-element vector by the rotation part and then adding the translation part as a separate step is really just assuming that the missing fourth component of the 3-element vector is unity. In order to handle the fourth row of the matrix correctly, you have to do the same assumption again, carry out the multiplication, and see how the bottom row affects the other three elements, as well as performing the final perspective division to ensure that the assumption that the fourth component really is unity even after the multiplication.

In the end, you really have to carry out a full 4-vector times 4x4-matrix multiplication, although you can assume that one element is unity and eliminate its multiplication with the corresponding elements of the matrix, and just add them. Edited by Brother Bob

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thank you for the insight. I'm still re-reading this a few times to let it sink in.

one problem I'm having is trying to create a frustum from a unit cube by multiplying each of the cube's vertices by the inverse of a projection matrix (as I'm told that is how it's done) so I can do basic view-frustum culling with world objects. currently, the result I'm getting is not a frustum.

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okay, I think I understand everything you've said.

doing this wihtout inverting for the first try:

I've got a vector (1,2,3) and I want to multiply it by my perspective matrix:

0.75 0 0 0
0 1 0 0
0 0 -1.0001 -0.20001
0 0 -1 0

after applying rotation and translation, I have this:

0.75,2,-3.20031

and then to apply the projection division... this is where I'm not totally sure how to apply it.. but I think I would end up with a Vec4:

0.75,2,-3.20031,-1

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I addressed that in my last paragraph; you have to perform a full 4-dimensional multiplication because you cannot multiply a 3-dimensional by a 4x4 matrix. You have to expand the multiplication using a full 4-dimensional vector.

Here's your matrix and vector and the product of the two.
 >> M M = 0.7500 0 0 0 0 1.0000 0 0 0 0 -1.0001 -0.2000 0 0 -1.0000 0 >> v v = 1 2 3 1 >> p = M*v p = 0.7500 2.0000 -3.2003 -3.0000 
See how the fourth element of the vector p is -3.0? That's because your 3-dimensional vector is actually a 4-dimensional vector with an implicit element at the end with a value of 1.0.

The perspective division is just dividing all elements of the vector by the fourth element:
 >> p./p(4) ans = -0.2500 -0.6667 1.0668 1.0000 
So your resulting projected 3-dimensional vector is (-0.2500, -0.6667, 1.0668). Edited by Brother Bob

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oh wow, that's easy. thank you very much! sometimes it takes baby-speak and sock puppets to explain things to me

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I'm curious... what program are you using there in the last post? has some interesting notation

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My guess would be MatLab or Octave.

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My guess would be MatLab or Octave.

It's Matlab, to be specific.

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I am using Octave for this, and I can recommend it. I attached a zip file to this post that contains 4 simple macros to help you experiment with matrices. It helped me to quickly experiment and gain understanding.
rot: Create a rotation matrix.
scale(x,y,z): Create a scaling matrix
transl(x,y,z): Create a translation matrix
Shearz: Create a shear matrix in z.

Examples:
octave:3> scale(1,2) ans = 1 0 0 0 0 2 0 0 0 0 1 0 0 0 0 1 octave:4> v=[1;2;3;1] v = 1 2 3 1 octave:6> scale(1,2)*v ans = 1 4 3 1 octave:7> rot(pi/2) ans = 1.00000 0.00000 0.00000 0.00000 0.00000 0.00000 -1.00000 0.00000 -0.00000 1.00000 0.00000 0.00000 0.00000 0.00000 0.00000 1.00000 octave:8> rot(pi/2)*v ans = 1 -3 2 1 octave:9> inverse(rot(pi/2)) ans = 1.00000 0.00000 -0.00000 -0.00000 0.00000 0.00000 1.00000 -0.00000 0.00000 -1.00000 0.00000 -0.00000 0.00000 0.00000 0.00000 1.00000 octave:11> T=transl(1); octave:19> S=scale(2); octave:20> S*T*v ans = 4 2 3 1 octave:21> T*S*v ans = 3 2 3 1

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thank you, larspensjo. I was delighted to find octave available for my linux distro. but how about projection/perspective matrices?

I presume the way to invert the perspective section of a matrix is to just negate the values, just the same as negating the translation parts. is this correct?

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thank you, larspensjo. I was delighted to find octave available for my linux distro. but how about projection/perspective matrices?

I presume the way to invert the perspective section of a matrix is to just negate the values, just the same as negating the translation parts. is this correct?

You cannot invert the individual sections of a matrix just like that. It just happens to work for translation under very specific circumstances. Likewise, you can invert other sections under other specific conditions.

If you have a matrix consisting of the perspective division component only, then you can invert it by negating the bottom row just like you do with translation. But if you have other components of the projection matrix, and a usual projection matrix does have both translation and non-uniform scaling, then you cannot do that anymore.

But take a look at how OpenGL's matrices are commonly designed here in appendix F. It lists their inverse also.

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But take a look at how OpenGL's matrices are commonly designed here in appendix F. It lists their inverse also.

I tried implementing my own fucntions to generate a matrix based on those equations, as well as an inverse:

Multiplying a matrix together with it's own inverse should result in an identity matrix. I'm getting mostly identity, except col 3 row 4 is always -5.9, and col 4 row 3 is always -1.2. I've tripple-checked that my matrices match the ones in the image.

I think the problem is in my matrix multiplication. I know how to multiply the 3x3 rotation section of the matrix and then add the translation, but what do I do with the perspective section?

Edit: I've been googling and even looked into a few CG programming books. nobody seems to say how to handle the bottom row of a GL 4x4 when multiplying two matrices together... Edited by caibbor

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You have two 4x4 matrices so you have to multiply them as 4x4 matrices. The bottom row is just like any other row in the matrix, there is nothing special about it at all.

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alright, then riddle me this.

(all in column-major order)

The projection matrix I created is:
0.074978 0.000000 0.000000 0.000000 0.000000 0.099970 0.000000 0.000000 0.000000 0.000000 -1.000100 -1.000000 0.000000 0.000000 -0.200010 0.000000

It's inverse I calculated is:
13.337285 0.000000 0.000000 0.000000 0.000000 10.002963 0.000000 0.000000 0.000000 0.000000 0.000000 -4.999750 0.000000 0.000000 -1.000000 20001000.000000

an multiplying those matrices together should be identy, but instead I get:
1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 -20000994.000000 1.000000

All code related to this is shown below. I've been up and down and all the methods, as far as I can tell, look correct.
[source lang="cpp"]// Mat4f class is a 4x4 matrix of floats.
// Mat4f::data is a float[16], and is column-major

// returns float& intentionally, method is private
inline float& Mat4f::M( const int col, const int row ) {
assert( col < dim && row < dim && col >= 0 && row >= 0);
return data[row+col*4];
}

void Mat4f::Multiply( const Mat4f& mat, Mat4f& out ) const {
assert ( &mat != &out );
int r,c;

for ( c=0; c<4; c++ ) {
for ( r=0; r<4; r++ ) {
out.M(c,r) =
M(r,0) * mat.M(0,c) +
M(r,1) * mat.M(1,c) +
M(r,2) * mat.M(2,c) +
M(r,3) * mat.M(3,c);
}
}
}

// calculation from: http://www.glprogramming.com/red/images/Image23.gif
void my_glFrustum( float l, float r, float b, float t, float n, float f, Mat4f& out ) {
float n2 = n * 2.0f;
out.data[0]=n2/(r-l);
out.data[1]=0.0f;
out.data[2]=0.0f;
out.data[3]=0.0f;

out.data[4]=0.0f;
out.data[5]=n2/(t-b);
out.data[6]=0.0f;
out.data[7]=0.0f;

out.data[8]=(r+l)/(r-l);
out.data[9]=(t+b)/(t-b);
out.data[10]=-(f+n)/(f-n);
out.data[11]=-1.0f;

out.data[12]=0.0f;
out.data[13]=0.0f;
out.data[14]=-(n2*f)/(f-n);
out.data[15]=0.0f;
}

// calculation from: http://www.glprogramming.com/red/images/Image23.gif
void my_glFrustum_inv( float l, float r, float b, float t, float n, float f, Mat4f& out ) {
float n2 = n * 2.0f;
out.data[0]=(r-l)/n2;
out.data[1]=0.0f;
out.data[2]=0.0f;
out.data[3]=0.0f;

out.data[4]=0.0f;
out.data[5]=(t-b)/n2;
out.data[6]=0.0f;
out.data[7]=0.0f;

out.data[8]=0.0f;
out.data[9]=0.0f;
out.data[10]=0.0f;
out.data[11]=-(f-n)/(n2*f);

out.data[12]=(r+l)/n2;
out.data[13]=(t+b)/n2;
out.data[14]=-1.0f;
out.data[15]=(f+n)/n2*f;
}

void my_gluPerspective( float fov, float x,float y,float near,float far, Mat4f& out, bool invert = false );
void my_gluPerspective( float fov, float x,float y,float near,float far, Mat4f& out, bool invert ) {
// inspired by http://www.cse.unsw....e/frustsrc.html
float aspect = x / y;
float t = 1.0f/tanf(fov * 3.141f / 360.0f);
if ( invert ) {
my_glFrustum_inv(-t * aspect, t * aspect, -t, t, near, far, out);
} else {
my_glFrustum(-t * aspect, t * aspect, -t, t, near, far, out);
}
}

inline void my_gluPerspective_inv( float fov, float x,float y,float near,float far, Mat4f& out ) {
my_gluPerspective( fov, x, y, near, far, out, true );
}

int main ( void ) {
Mat4f should_be_identity;
Mat4f projection;
Mat4f projection_inverse;

my_gluPerspective(90,800,600,0.1f,2000,projection);
my_gluPerspective_inv(90,800,600,0.1f,2000,projection_inverse);

projection.Multiply(projection_inverse, should_be_identity);
for ( int i=0; i<16; i++ )
printf("%f ", should_be_identity.data );

/*
expected output:
1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 1.000000

actual output:
1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 -20000994.000000 1.000000
*/
return 0;
}
[/source] Edited by caibbor

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Your element 15 of the inverse is incorrect. The denominator is missing a parenthesis to ensure that the multiplication by f doesn't end up in the numerator.

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"I always do that. I always mess up some mundane detail." - Michael Bolton, Office Space

thanks.

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• This article uses material originally posted on Diligent Graphics web site.
Introduction
Graphics APIs have come a long way from small set of basic commands allowing limited control of configurable stages of early 3D accelerators to very low-level programming interfaces exposing almost every aspect of the underlying graphics hardware. Next-generation APIs, Direct3D12 by Microsoft and Vulkan by Khronos are relatively new and have only started getting widespread adoption and support from hardware vendors, while Direct3D11 and OpenGL are still considered industry standard. New APIs can provide substantial performance and functional improvements, but may not be supported by older hardware. An application targeting wide range of platforms needs to support Direct3D11 and OpenGL. New APIs will not give any advantage when used with old paradigms. It is totally possible to add Direct3D12 support to an existing renderer by implementing Direct3D11 interface through Direct3D12, but this will give zero benefits. Instead, new approaches and rendering architectures that leverage flexibility provided by the next-generation APIs are expected to be developed.
There are at least four APIs (Direct3D11, Direct3D12, OpenGL/GLES, Vulkan, plus Apple's Metal for iOS and osX platforms) that a cross-platform 3D application may need to support. Writing separate code paths for all APIs is clearly not an option for any real-world application and the need for a cross-platform graphics abstraction layer is evident. The following is the list of requirements that I believe such layer needs to satisfy:
Lightweight abstractions: the API should be as close to the underlying native APIs as possible to allow an application leverage all available low-level functionality. In many cases this requirement is difficult to achieve because specific features exposed by different APIs may vary considerably. Low performance overhead: the abstraction layer needs to be efficient from performance point of view. If it introduces considerable amount of overhead, there is no point in using it. Convenience: the API needs to be convenient to use. It needs to assist developers in achieving their goals not limiting their control of the graphics hardware. Multithreading: ability to efficiently parallelize work is in the core of Direct3D12 and Vulkan and one of the main selling points of the new APIs. Support for multithreading in a cross-platform layer is a must. Extensibility: no matter how well the API is designed, it still introduces some level of abstraction. In some cases the most efficient way to implement certain functionality is to directly use native API. The abstraction layer needs to provide seamless interoperability with the underlying native APIs to provide a way for the app to add features that may be missing. Diligent Engine is designed to solve these problems. Its main goal is to take advantages of the next-generation APIs such as Direct3D12 and Vulkan, but at the same time provide support for older platforms via Direct3D11, OpenGL and OpenGLES. Diligent Engine exposes common C++ front-end for all supported platforms and provides interoperability with underlying native APIs. It also supports integration with Unity and is designed to be used as graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. Full source code is available for download at GitHub and is free to use.
Overview
Diligent Engine API takes some features from Direct3D11 and Direct3D12 as well as introduces new concepts to hide certain platform-specific details and make the system easy to use. It contains the following main components:
Render device (IRenderDevice  interface) is responsible for creating all other objects (textures, buffers, shaders, pipeline states, etc.).
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API Basics
Creating Resources
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TextureDesc TexDesc; TexDesc.Name = "My texture 2D"; TexDesc.Type = TEXTURE_TYPE_2D; TexDesc.Width = 1024; TexDesc.Height = 1024; TexDesc.Format = TEX_FORMAT_RGBA8_UNORM; TexDesc.Usage = USAGE_DEFAULT; TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS; TexDesc.Name = "Sample 2D Texture"; m_pRenderDevice->CreateTexture( TexDesc, TextureData(), &m_pTestTex ); If native API supports multithreaded resource creation, textures and buffers can be created by multiple threads simultaneously.
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Initializing the Pipeline State
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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:
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// 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.
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:
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.
• By reenigne
For those that don't know me. I am the individual who's two videos are listed here under setup for https://wiki.libsdl.org/Tutorials
I also run grhmedia.com where I host the projects and code for the tutorials I have online.
Recently, I received a notice from youtube they will be implementing their new policy in protecting video content as of which I won't be monetized till I meat there required number of viewers and views each month.

Frankly, I'm pretty sick of youtube. I put up a video and someone else learns from it and puts up another video and because of the way youtube does their placement they end up with more views.
Even guys that clearly post false information such as one individual who said GLEW 2.0 was broken because he didn't know how to compile it. He in short didn't know how to modify the script he used because he didn't understand make files and how the requirements of the compiler and library changes needed some different flags.

At the end of the month when they implement this I will take down the content and host on my own server purely and it will be a paid system and or patreon.

I get my videos may be a bit dry, I generally figure people are there to learn how to do something and I rather not waste their time.
I used to also help people for free even those coming from the other videos. That won't be the case any more. I used to just take anyone emails and work with them my email is posted on the site.

I don't expect to get the required number of subscribers in that time or increased views. Even if I did well it wouldn't take care of each reoccurring month.
I figure this is simpler and I don't plan on putting some sort of exorbitant fee for a monthly subscription or the like.
I was thinking on the lines of a few dollars 1,2, and 3 and the larger subscription gets you assistance with the content in the tutorials if needed that month.
Maybe another fee if it is related but not directly in the content.
The fees would serve to cut down on the number of people who ask for help and maybe encourage some of the people to actually pay attention to what is said rather than do their own thing. That actually turns out to be 90% of the issues. I spent 6 hours helping one individual last week I must have asked him 20 times did you do exactly like I said in the video even pointed directly to the section. When he finally sent me a copy of the what he entered I knew then and there he had not. I circled it and I pointed out that wasn't what I said to do in the video. I didn't tell him what was wrong and how I knew that way he would go back and actually follow what it said to do. He then reported it worked. Yea, no kidding following directions works. But hey isn't alone and well its part of the learning process.

So the point of this isn't to be a gripe session. I'm just looking for a bit of feed back. Do you think the fees are unreasonable?
Should I keep the youtube channel and do just the fees with patreon or do you think locking the content to my site and require a subscription is an idea.

I'm just looking at the fact it is unrealistic to think youtube/google will actually get stuff right or that youtube viewers will actually bother to start looking for more accurate videos.

• i got error 1282 in my code.
#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.

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• 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.

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