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OpenGL world to local rotations

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In opengl I rotate objects in world space:

glRotatef(myObject.zRot, 0, 0, 1);
glRotatef(myObject.xRot, 1, 0, 0);
glRotatef(myObject.yRot, 0, 1, 0);


There is a way to find the object local angles of rotation?

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In opengl I rotate objects in world space:

glRotatef(myObject.zRot, 0, 0, 1);
glRotatef(myObject.xRot, 1, 0, 0);
glRotatef(myObject.yRot, 0, 1, 0);


There is a way to find the object local angles of rotation?


Look into quaternions. You can use that rotation matrix to extract a quat and then get eular angles (xyz).
There is a quaternion lib in my library.
There is also a function for extracting angles directly from a rotation matrix.

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In opengl I rotate objects in world space:

glRotatef(myObject.zRot, 0, 0, 1);
glRotatef(myObject.xRot, 1, 0, 0);
glRotatef(myObject.yRot, 0, 1, 0);


OpenGL does not work in world space. IF your modelview was still identity, the very first rotation will happen to in world space, but only because local and global are still the same. Every rotation after that is using the local coordinate system resulting from your previous transformations. If you want to use global coordinates, you have to change the order of the matrix multiplication (ie. do it manually, because OpenGL will always do modelview = rotationMatrix * modelview, when what you want is modelview = modelview * rotationMatrix; ).

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[quote name='Alessandro' timestamp='1318032168' post='4870317']
In opengl I rotate objects in world space:

glRotatef(myObject.zRot, 0, 0, 1);
glRotatef(myObject.xRot, 1, 0, 0);
glRotatef(myObject.yRot, 0, 1, 0);


OpenGL does not work in world space. IF your modelview was still identity, the very first rotation will happen to in world space, but only because local and global are still the same. Every rotation after that is using the local coordinate system resulting from your previous transformations. If you want to use global coordinates, you have to change the order of the matrix multiplication (ie. do it manually, because OpenGL will always do modelview = rotationMatrix * modelview, when what you want is modelview = modelview * rotationMatrix; ).
[/quote]

Sorry for the confusion. Yes opengl works in local space. I do have a quaternion library but I don't know the math of how would I go from local angles to world space, using matrices. Any chance to have some pseudo-code?

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Here is the code I came up with. I'm still not sure I'm extracting angles correctly from the final step.<br><br>



float xRot=45.0*DEG_TO_RAD;
float yRot=30.0*DEG_TO_RAD;
float zRot=22.0*DEG_TO_RAD;

// build rotateX matrix
matX= new float[16];
matX[5] = cosf(xRot);
matX[6] = -sinf(xRot);
matX[9] = -matX[6];
matX[10] = matX[5];

// build rotateY matrix
matY= new float[16];
matY[0] = cosf(yRot);
matY[2] = sinf(yRot);
matY[8] = -matY[2];
matY[10] = matY[0];

// build rotateZ matrix
matZ= new float[16];
matZ[0] = cosf(zRot);
matZ[1] = sinf(zRot);
matZ[4] = -matZ[1];
matZ[5] = matZ[0];

matXY=new float[16];
matXYZ=new float[16];

matXY= matrixMultiply(matX, matY);
matXYZ=matrixMultiply(matXY, matZ); //calculate final rotation matrix matXYZ

float *modelview;
modelview= new float[16];
glGetFloatv( GL_MODELVIEW_MATRIX, modelview ); // Get the current MODELVIEW matrix from OpenGL

float *worldRotMatrix;
worldRotMatrix=new float[16];
worldRotMatrix=matrixMultiply(modelview,matXYZ); // this should be the final rotation matrix, in world space

angle_y = -asin( worldRotMatrix[2]); /* Calculate Y-axis angle */
float C = cos( angle_y );
if ( fabs( C ) > 0.005 ) /* Gimball lock? */
{
tr_x = worldRotMatrix[10] / C; /* No, so get X-axis angle */
tr_y = -worldRotMatrix[6] / C;
angle_x = atan2( tr_y, tr_x ) ;
tr_x = worldRotMatrix[0] / C; /* Get Z-axis angle */
tr_y = -worldRotMatrix[1] / C;
angle_z = atan2( tr_y, tr_x ) ;
}
else /* Gimball lock has occurred */
{
angle_x = 0; /* Set X-axis angle to zero */
tr_x = worldRotMatrix[5]; /* And calculate Z-axis angle */
tr_y = worldRotMatrix[4];
angle_z = atan2( tr_y, tr_x ) ;
}




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Forgot to show the matrixMultiply function:


float* matrixMultiply(float* m1, float* m2)
{
float *finalMat;
finalMat=new float[16];
matrixIdentity(finalMat);
// Fisrt Column
finalMat[0] = m1[0]*m2[0] + m1[4]*m2[1] + m1[8]*m2[2] + m1[12]*m2[3];
finalMat[1] = m1[1]*m2[0] + m1[5]*m2[1] + m1[9]*m2[2] + m1[13]*m2[3];
finalMat[2] = m1[2]*m2[0] + m1[6]*m2[1] + m1[10]*m2[2] + m1[14]*m2[3];
finalMat[3] = m1[3]*m2[0] + m1[7]*m2[1] + m1[11]*m2[2] + m1[15]*m2[3];

// Second Column
finalMat[4] = m1[0]*m2[4] + m1[4]*m2[5] + m1[8]*m2[6] + m1[12]*m2[7];
finalMat[5] = m1[1]*m2[4] + m1[5]*m2[5] + m1[9]*m2[6] + m1[13]*m2[7];
finalMat[6] = m1[2]*m2[4] + m1[6]*m2[5] + m1[10]*m2[6] + m1[14]*m2[7];
finalMat[7] = m1[3]*m2[4] + m1[7]*m2[5] + m1[11]*m2[6] + m1[15]*m2[7];

// Third Column
finalMat[8] = m1[0]*m2[8] + m1[4]*m2[9] + m1[8]*m2[10] + m1[12]*m2[11];
finalMat[9] = m1[1]*m2[8] + m1[5]*m2[9] + m1[9]*m2[10] + m1[13]*m2[11];
finalMat[10] = m1[2]*m2[8] + m1[6]*m2[9] + m1[10]*m2[10] + m1[14]*m2[11];
finalMat[11] = m1[3]*m2[8] + m1[7]*m2[9] + m1[11]*m2[10] + m1[15]*m2[11];

// Fourth Column
finalMat[12] = m1[0]*m2[12] + m1[4]*m2[13] + m1[8]*m2[14] + m1[12]*m2[15];
finalMat[13] = m1[1]*m2[12] + m1[5]*m2[13] + m1[9]*m2[14] + m1[13]*m2[15];
finalMat[14] = m1[2]*m2[12] + m1[6]*m2[13] + m1[10]*m2[14] + m1[14]*m2[15];
finalMat[15] = m1[3]*m2[12] + m1[7]*m2[13] + m1[11]*m2[14] + m1[15]*m2[15];

return finalMat;
}

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If you understand the dot product and know how to use it to find angles between vectors:

After you do those 3 global rotations you get a matrix that shows the new x,y,z vectors for your object. So by drawing your object with the identity matrix it is probably aligned with the global vectors (right = x, y = top, forward = z or negative z). Those 3 vectors now equal the 3 columns in your matrix after doing global rotations. In otherwords, The identity matrix gives you x,y,z axis, what do they map to now: column0,1,2 of your matrix. So do a dot product between the old x and new x, old y and new y, old z and new z. And you can figure out that but.

I assume that is what you want, but you should be knowing the local rotations (yaw,pitch,roll). I do what you do, I align all models on the z axis, that way I can do z rotation first, and then the x,y rotations are the ones the figure out the heading direction of the object. I think I just dont understand your problem though.

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Sorry, instead of writing code perhaps I had to explain more in detail what I'm trying to do.
I have a simple opengl application where I load and display .obj files. The application allows also to position, scale and rotate those models using the mouse. All those transformations happen in local space.
The application allows to export the above data in a .txt file, with the following scheme:

obj file | xRot | yRot | zRot | xPos | yPos | zPos

Later on, in a separate, commercial application, I read this .txt file and I recreate the scene, loading sequentually the obj's files and applying the transformation values read from the .txt file.
Problem is, that the commercial application perform rotations in world space, while the angles that I "exported" are in local space.

So, what I'm trying to do is to convert those angles from local to world space so that the objects are properly rotated in the commercial application.

I hope I could explain myself better...

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You should be able to use the local xyz rotations to compute what the object would draw like relative to its own Identity/Local space, Then apply the transform that makes the object be a certain way globally. Should be able to just multiply both matrices. That would give you the final matrix it should look like to draw with given the vertex data in local space. With that matrix, you could just dot product all vectors in that matrix (column0,1,2) with the regular world space vectors (1,0,0 0,1,0, 0,0,1) with their new representations column0,1,2 and that would give you the angle that the object is drawing at relative to the regular world axis.

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Thanks dpadam450, so the pseudo-code would look like this:

1) build the object local space matrix
2) get the current MODELVIEW matrix from OpenGL
3) build final matrix multiplying the MODELVIEW by the local space matrix (and I think I arrived at this point in previous code I posted)
4) dot product the vectors defined by columns 0,1,2 of the final matrix, by the corresponding regular world space vectors (1,0,0 0,1,0, 0,0,1)
5) extract euler angles from this last resulting matrix.

Would that work? Any comments also from others?

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Again for mine, I make sure that any game object in my game has NO transform, meaning it is drawn with the Identity matrix, and when it is drawn with the identity matrix I make sure it is fixed so that the xyz locally are the xyz globally. Meaning my model in Blender has up = y, x = right and negative z = forward for all models. If I rotate the object 30 degrees on the y-axis in my engine, I know that its local forward vector from export and in my game engine are going to be the exact same x,y,z components. So local = global. But again if your model already has a transform when exported, you should erase it if u can and just rotate the vertices and not the objects matrix. What exactly is rotx,y,z local to anyway? I can spin my body in any direction and my right relative to myself is still just "my right". I think what you have is a global transform of your model in your modeling application.

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In a different way of saying what does rotx mean relative to local: stand up right now close ur eyes and spin in circles then stop. What is your rotation x relative locally to you ?..........nothing. You could say it is 100 degrees relative to my old localness, or 20 degrees on my world x. So what you are exporting is probably rotx relative to world or something, the model exported shouldnt have any. If this is an instance that you have rotated then, if you make its local original system the identity matrix then local = global.

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Later on, in a separate, commercial application, I read this .txt file and I recreate the scene, loading sequentually the obj's files and applying the transformation values read from the .txt file.
Problem is, that the commercial application perform rotations in world space, while the angles that I "exported" are in local space.


Are you sure that it's not simply a matter of one application applying rotations in another order than the second app? The only difference between rotation around a local or global axis is whether you multiply like
local: matrix = rotation * matrix
global: matrix = matrix * rotation

I also really dislike storing orientations as Euler angles. It's completely useless without knowing in which order they need to be applied.

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Are you sure that it's not simply a matter of one application applying rotations in another order than the second app? The only difference between rotation around a local or global axis is whether you multiply like
local: matrix = rotation * matrix
global: matrix = matrix * rotation


Yes, it's exactly like that. All I need to do is to convert the values of local rotations in Application1 to world rotation values, so that Application2 can use those values and display objects with the same orientation.

So, say in Application1 I have an object rotated in local space, what I'm doing to convert local angles to world angles is:

1) build the rotation matrix out of object rotation angles
2) multiply the modelview by the object rotation matrix built at step1
3) get the euler angles from the above matrix

The angles computed this way, and I applied to Application2 are not working (i.e. the object orientation doesn't match the one in Application1)
This problem is driving me nut.

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And what drives me crazy is that I'm so dumb to figure out what it seems to be such an easy problem. I mean, let's forget opengl for a moment.
I have an object rotated in local space as follows:

pitch=45, yaw=30, roll=15

Given that world axis are [1,0,0] [0,1,0] [0,0,1]

Now, let's calculate world angles out of it... what is the math beyond it?

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And what drives me crazy is that I'm so dumb to figure out what it seems to be such an easy problem. I mean, let's forget opengl for a moment.
I have an object rotated in local space as follows:

pitch=45, yaw=30, roll=15

Given that world axis are [1,0,0] [0,1,0] [0,0,1]

Now, let's calculate world angles out of it... what is the math beyond it?


The math is that your problem has several potential solutions with only one of them being correct and without knowing the ORDER in which pitch/yaw/roll are supposed to be applied you can only try until it fits. Three angles alone do NOT describe a unique orientation, but six possible ones. That has nothing to do with local or global space (or rather: one of those potential orders already IS the equivalent of using world instead of local axes).

Also, an angle is an angle and doesn't care about local or whatever space. If wavefront does pitch-yaw-roll using object local axes and you insist on using world axes, you do roll-yaw-pitch and are done with it. Why? Because one does
totalRotation = rotation(roll, 0,0,1) * rotation(yaw, 0,1,0) * rotation(pitch, 1,0,0)
and the other does
totalRotation = rotation(pitch, 1,0,0) * rotation(yaw, 0,1,0) * rotation(roll, 0,0,1)

At no point does it make sense to actually calculate an objects local x,y,z axis and use that for a rotation, since this happens "automatically" if you multiply in the right order.

Assuming your application is exporting angles that are based on your own order (localX, localZ, localY = globalY, globalZ, globalX), what order is the OTHER application applying the rotations?

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To supplement Trienco's writings:

This code from the OP

glRotatef(myObject.zRot, 0, 0, 1);
glRotatef(myObject.xRot, 1, 0, 0);
glRotatef(myObject.yRot, 0, 1, 0);

means a combined rotation (written n the following using column vector notation as is usual when dealing with OpenGL)
R[sub]z[/sub] * R[sub]x[/sub] * R[sub]y[/sub]
Probing a rotation R * v of a vector v, one notices that any point that is part of the axis of rotation is mapped onto itself (0 is always such a point), regardless of R. Because a combined rotation like
v' = R[sub]z[/sub] * R[sub]x[/sub] * R[sub]y[/sub] * v
can be seen as
v[sub]1[/sub] = R[sub]y[/sub] * v
v[sub]2[/sub] = R[sub]x[/sub] * v[sub]1[/sub]
v' = R[sub]z[/sub] * v[sub]2[/sub]

I like to say that each particular rotation is done in a space that is coincident with the world space at the moment when the transformation is applied.

Now, you don't want to do so. You want to rotate around the axes that are coincident with the model space axes. So you have to ensure that the desired axis is coincident with the belonging "world axis" at the moment you want to apply the rotation. This is always true for the first rotation (y in this case).
R[sub]y[/sub] * v
But after that rotation the model space x axis isn't coincident with the world y axis any longer. Hence you need to "undo" the first rotation, apply the desired rotation then, and "redo" the first rotation:
R[sub]y[/sub] * R[sub]x[/sub] *
R[sub]y[/sub][sup]-1[/sup] *
( R[sub]y[/sub] * v ) = R[sub]y[/sub] * R[sub]x[/sub] *
v
Doing this a 2nd time for the 3rd rotation as well, yields in
R[sub]y[/sub] * R[sub]x[/sub] * R[sub]z[/sub] * v
what is obviously a combined rotation similarly to the original one but with a reversed order of matrices. Hence this rotation still uses the same "world axes", but due to its chosen order the effect is like rotating around the model axes. Notice please that the angles in use are not changed at all.


You can compute something like "world angles" from "local angles" if you want. You would do it by choosing the order for the local rotation and compute the result with known "local angles", e.g.
R := R[sub]y[/sub] * R[sub]x[/sub] * R[sub]z[/sub]
and compute the angles that are needed to get the same result but with the reverse order, i.e.
R[sub]z[/sub] * R[sub]x[/sub] * R[sub]y[/sub] = R
in this case. However, as Trienco already said, this is meaningless for the given problem.



P.S.: This editor is really a pain! It seems impossible to prevent it to switch some portions of the text into a bold appearance...

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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.
      Interoperability with native API provides access to the native buffer/texture objects and also allows creating Diligent Engine objects from native handles. It allows applications seamlessly integrate native API-specific code with Diligent Engine.
      Next-generation APIs allow fine level-control over how resources are allocated. Diligent Engine does not currently expose this functionality, but it can be added by implementing IResourceAllocator interface that encapsulates specifics of resource allocation and providing this interface to CreateBuffer() or CreateTexture() methods. If null is provided, default allocator should be used.
      Initializing the Pipeline State
      As it was mentioned earlier, Diligent Engine follows next-gen APIs to configure the graphics/compute pipeline. One big Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions etc.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings it is very easy to forget to set one of the states or assume the stage is already properly configured when in fact it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.
      Creating Shaders
      While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
      SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
      When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
      The following is an example of shader initialization:
      ShaderCreationAttribs Attrs; Attrs.Desc.Name = "MyPixelShader"; Attrs.FilePath = "MyShaderFile.fx"; Attrs.SearchDirectories = "shaders;shaders\\inc;"; Attrs.EntryPoint = "MyPixelShader"; Attrs.Desc.ShaderType = SHADER_TYPE_PIXEL; Attrs.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL; BasicShaderSourceStreamFactory BasicSSSFactory(Attrs.SearchDirectories); Attrs.pShaderSourceStreamFactory = &BasicSSSFactory; ShaderVariableDesc ShaderVars[] = {     {"g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},     {"g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},     {"g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC} }; Attrs.Desc.VariableDesc = ShaderVars; Attrs.Desc.NumVariables = _countof(ShaderVars); Attrs.Desc.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC; StaticSamplerDesc StaticSampler; StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR; StaticSampler.TextureName = "g_MutableTexture"; Attrs.Desc.NumStaticSamplers = 1; Attrs.Desc.StaticSamplers = &StaticSampler; ShaderMacroHelper Macros; Macros.AddShaderMacro("USE_SHADOWS", 1); Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4); Macros.Finalize(); Attrs.Macros = Macros; RefCntAutoPtr<IShader> pShader; m_pDevice->CreateShader( Attrs, &pShader );
      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.
    • 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. 
    • 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
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