[Discuss] Viewport matrix

[fatboy88]

I was looking at some shaders in the diesel engine there was one for viewport matrix so I investigated.

Viewport Transformation

shows how to set up a vp matrix and well im just wondering do guys think there would be a performance increase using it IF you create the matrix once and only call getviewport when the resolution changes? With it you now have another d3dxmatrixmultiply I'm just wonder if you think the performance effects are worth the trouble and matrixmultiply call. or just backing them up viewport and doing w2s manually w/o d3dxvec3project.

f(!Created)
  {
          D3DVIEWPORT9 viewPort;
          pDevice->GetViewport(&viewPort);

		  float CenterScreenX = viewPort.Width/2;
		  float CenterScreenY = viewPort.Height/2;
		  vP._11 =  CenterScreenX;
		  vP._22 = -CenterScreenY;
		  vP._33 = viewPort.MaxZ - viewPort.MinZ;
		  vP._41 = viewPort.X + CenterScreenX;
		  vP._42 = viewPort.Y + CenterScreenY;
		  vP._43 = viewPort.MinZ;
		  vP._44 = 1;
  
  Created = true;
  }

                         D3DXMatrixMultiply(&m1, &world, &view);
			 D3DXMatrixMultiply(&m2, &m1, &projection);
			 D3DXMatrixMultiply(&m3, &m2, &vP);
			 D3DXVec3TransformCoord(&vScreenCoord, &vWorldLocation, &m3);

if(vScreenCoord.z < 1){
text(x,y);
}

[CallMeEclipse]

Its probably better to only call it if the resolution changes, but you may as well try it and see how it works out either way.

[fatboy88]

Originally Posted by CallMeEclipse

Its probably better to only call it if the resolution changes, but you may as well try it and see how it works out either way.

ya thats how i already do it, I also do the projection like that and check if zooming/resolution change

backing up viewport and doing w2s manually w/o d3dxvec3project

tho i still go ahead and back up the entire proj matrix(plan on eliminating the matrix part also only did it cuz vertex & pixel shader ten to use only ViewProj matrix), and dont use world at all :x