evelyn4you

DX11 Constant Buffer binding ( how long does it remain )

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hi,

i have read very much about the binding of a constantbuffer to a shader but something is still unclear to me.

e.g. when performing :   vertexshader.setConstantbuffer ( buffer,  slot )

 is the buffer bound

a.  to the VertexShaderStage

or

b. to the VertexShader that is currently set as the active VertexShader

Is it possible to bind a constantBuffer to a VertexShader e.g. VS_A and keep this binding even after the active VertexShader has changed ?
I mean i want to bind constantbuffer_A  to VS_A, an Constantbuffer_B to VS_B  and  only use updateSubresource without using setConstantBuffer command every time.


Look at this example:

SetVertexShader ( VS_A )
updateSubresource(buffer_A)
vertexshader.setConstantbuffer ( buffer_A,  slot_A )

perform drawcall       ( buffer_A is used )

SetVertexShader ( VS_B )
updateSubresource(buffer_B)
vertexshader.setConstantbuffer ( buffer_B,  slot_A )

perform drawcall   ( buffer_B is used )

SetVertexShader ( VS_A )
perform drawcall   (now which buffer is used ??? )

 

I ask this question because i have made a custom render engine an want to optimize to

the minimum  updateSubresource, and setConstantbuffer  calls

 

 

 

 

 

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Bindings of constant buffers are separate and unrelated to the currently bound Vertex Shader.

When you bind a constant buffer you are binding it to the "pipeline", not to the currently set Vertex Shader. For that reason, you are free to set a constant buffer once and then repeatedly update its contents and change Vertex Shader without needing to rebind the constant buffer.

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You must consider the pipeline as a huge finite state machine:

(vertex shader program, vertex shader c|t|s registers, hull shader program, hull shader c|t|s registers, ...)

Note that this state also includes non-shader-related components such as rasterizer state (RS), blend state (OM) and depth-stencil state (OM).

As long as you do not rebind a component of the state, the currently bound component is used. The shader program and shader registers are separate components of the state. So if you bind a constant buffer (c register), sampler state (s state), etc. to a shader stage and you do not rebind these slots, all bindings will be persistent (independent of which shader program is bound).

 

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