Game Development Reference
In-Depth Information
two transformation matrices for processing vertex positions into screen space and
vertex normals from object space into world space. Defining a constant buffer for
Direct3D 11 is done by filling in the
D3D11_BUFFER_DESC
structure and sending
the result into
ID3D11Device::CreateBuffer()
. This is simply creating a data
buffer with a size sufficient for the data we
re going to copy into it during rendering.
As you might expect, the definition for the
ConstantBuffer_Matrices
is just the
two transform matrices the vertex shader needs:
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struct ConstantBuffer_Matrices
{
Mat4x4 m_WorldViewProj;
Mat4x4 m_World;
};
The results are stored in the
m_pcbVSMatrices
member of the class. The two C++
structures referenced in the
D3D11_BUFFER_DESC
for material and lighting are
defined as follows:
struct ConstantBuffer_Material
{
Vec4 m_vDiffuseObjectColor;
Vec4 m_vAmbientObjectColor;
BOOL m_bHasTexture;
Vec3 m_vUnused;
};
struct ConstantBuffer_Lighting
{
Vec4 m_vLightDiffuse[MAXIMUM_LIGHTS_SUPPORTED];
Vec4 m_vLightDir[MAXIMUM_LIGHTS_SUPPORTED];
Vec4 m_vLightAmbient;
UINT m_nNumLights;
Vec3 m_vUnused;
};
There is a notable difference in these structures from the
ConstantBuffer_
Matrices
structure. At the end of each one, there is a
Vec3 m_vUnused
member.
The reason for this is that in each case, the previous member occupies only one byte
of the structure, leaving it at a size that can
'
t be properly aligned. GPU hardware is
notoriously picky about the size of structures, and if you don
'
t send data to them
aligned on 16-byte boundaries, you
'
ll get an
E_INVALIDARG
error coming back
from the call to
CreateBuffer()
.
So here
s a quick review. The shader source code was loaded, compiled, and created
ready to use for rendering. The vertex layout was defined. The constant buffers for
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