Vertex Shaders - Prt1 - Basics
by bkenwright@xbdev.net
While this might not seem very exciting - it's a very important first step in shader programming - shader assembly to pass the vertex positions onto the output.
This little function is called over and over again, and does the rendering of our simple triangle... notice how all our vertex shader code is all in this one function...I did that so you could see the birth and death of how it works in one easy step.... eventually you could put the creation..and destruction code in seperate function..etc...and optimise your code for better performance
////////////////////////////////////////////////////////////////////////////////////
// \\
// This little function is called over and over again, and does the rendering of \\
// our simple triangle... notice how all our vertex shader code is all in this \\
// one function...I did that so you could see the birth and death of how it works \\
// in one easy step.... eventually you could put the creation..and destruction \\
// code in seperate function..etc...and optimise your code for better performance \\
// ... \\
// \\
//\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
void Render()
{
if(!g_pd3dDevice)return;
//<-------------------Start of our vertex shader code-------------------------->
const char SimpleShader[] =
{
"vs.1.1 // Shader version 1.1 \n"
"mov oPos, v0 // oPos-Output register, v0-Input register\n"
};
DWORD dwDecl[] =
{
D3DVSD_STREAM(0),
D3DVSD_REG(D3DVSDE_POSITION, D3DVSDT_FLOAT2),
D3DVSD_END()
};
DWORD dwShaderID;
ID3DXBuffer* pVS;
D3DXAssembleShader( SimpleShader, sizeof(SimpleShader)-1,
0, NULL, &pVS, NULL );
g_pd3dDevice->CreateVertexShader(dwDecl, (DWORD*)pVS->GetBufferPointer(),
&dwShaderID, 0);
g_pd3dDevice->SetVertexShader( dwShaderID );
// Don't forget to put these lines in your code...I've added them to the bottom
// of the function!...always release resources after creating them.
//g_pd3dDevice->DeleteVertexShader(dwDecl);
//pVS->Release();
//<-------------------End of our vertex shader code---------------------------->
struct stVert
{
FLOAT x, y, z; // D3DFVF_XYZ
};
UINT myFVFFormat = D3DFVF_XYZ ;
stVert myBox[]=
{
{-0.5f, -0.5f, 0.0f},
{ 0.5f, 0.5f, 0.0f},
{-0.5f, 0.5f, 0.0f},
{-0.5f, -0.5f, 0.0f},
{ 0.5f, 0.5f, 0.0f},
{ 0.5f, -0.5f, 0.0f}
};
IDirect3DVertexBuffer8 * pVertexBuffer;
g_pd3dDevice->CreateVertexBuffer( 6*sizeof(stVert), 0,
myFVFFormat, D3DPOOL_MANAGED, &pVertexBuffer );
unsigned char *p;
pVertexBuffer->Lock(0,0, &p, 0);
memcpy(p, myBox, 6*sizeof(stVert) );
pVertexBuffer->Unlock();
//Turn off lighting becuase we are specifying that our vertices have colour
g_pd3dDevice->SetRenderState( D3DRS_LIGHTING, FALSE);
g_pd3dDevice->SetRenderState( D3DRS_ZENABLE, TRUE );
g_pd3dDevice->SetRenderState( D3DRS_CULLMODE, D3DCULL_NONE);
// Clear the backbuffer and the zbuffer
g_pd3dDevice->Clear( 0, NULL, D3DCLEAR_TARGET|D3DCLEAR_ZBUFFER,
D3DCOLOR_XRGB(0x00,0x00,0xff), 1.0f, 0 );
// Draw our triangle.
g_pd3dDevice->SetStreamSource(0, pVertexBuffer, sizeof(stVert));
//<-------------------Using our Vertex Shader Here ---------------------------->
g_pd3dDevice->SetVertexShader( dwShaderID );
g_pd3dDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 2);
// End the scene
g_pd3dDevice->EndScene();
// Present the backbuffer contents to the display
g_pd3dDevice->Present( NULL, NULL, NULL, NULL );
g_pd3dDevice->DeleteVertexShader(dwShaderID);
pVS->Release();
pVertexBuffer->Release();
}
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