Help with DirectX Transforms

Graphics and GPU Programming Programming

Started by pdugan October 21, 2005 11:36 AM

2 comments, last by dalep 18 years, 6 months ago

pdugan

122

Author

October 21, 2005 11:36 AM

I need some help with my DirectX transforms. I have a function that displays the axis, like so.


  Vertex verts[] = {
    Vertex(0,0,0,0,0,0xffff0000),
    Vertex(3,0,0,0,0,0xffff0000),
    Vertex(0,0,0,0,0,0xff00ff00),
    Vertex(0,3,0,0,0,0xff00ff00),
    Vertex(0,0,0,0,0,0xff00ffff),
    Vertex(0,0,3,0,0,0xff00ffff)
  };
  vertexBuffer.Write(verts, 6);
  vertexBuffer.SetAsSource();
  pd3dDevice->DrawPrimitive( D3DPT_LINELIST, 0, 6 );

So far so good, displays the axis looking down the z axis. Now, when I apply my transforms, I see absolutely nothing. Nada. Zip.


  D3DXMATRIXA16 matWorld;
  D3DXMatrixRotationY( &matWorld, timeGetTime()/1000.0f );
  pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );

  D3DXVECTOR3 vEyePt( 0.0f, 3.0f,-5.0f );
  D3DXVECTOR3 vLookatPt( 0.0f, 0.0f, 0.0f );
  D3DXVECTOR3 vUpVec( 0.0f, 1.0f, 0.0f );
  D3DXMATRIXA16 matView;
  D3DXMatrixLookAtLH( &matView, &vEyePt, &vLookatPt, &vUpVec );
  pd3dDevice->SetTransform( D3DTS_VIEW, &matView );

  D3DXMATRIXA16 matProj;
  D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 1.0f, 1.0f, 100.0f );
  pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj );

Any idea what I'm doing wrong?

"a riddle wrapped in a mystery inside an enigma" - Churchill

Armadon

1,091

October 21, 2005 12:02 PM

There are a few things you will need to check.
Is your camera (view) pointing in the right direction.
Your view you can think of as being a camera. If your object is outside of the camera's view you won't be able to see it.

Try changing the D3DXVECTOR3 vEyePt( 0.0f, 3.0f,-5.0f ) to D3DXVECTOR3 vEyePt( 0.0f, 0.0f, -5.0f ).

With that said make sure that your object isn't outside of the clipping planes. In your case it's probably not out of the clipping planes at all but it's nice to note. Change D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 1.0f, 1.0f, 100.0f ) to D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 1.0f, 1.0f, 1000.0f ) as it will help you in the long run.

Also when doing this type of setup it's generally good practise to setup the Projection and View transformation matrices and setting them in the init function of your engine/renderer as they don't usually change very often if not at all. Then when you render objects try and associate objects with a world transformation matrix as this locates the object in the world.

Some simple steps to follow.
1) Update world transformation matrix for your axis
2) Set the world transformation matrix for your axis
3) Render your axis.

I hope this helps.
Take care.

Source

272

October 21, 2005 01:48 PM

I haven't had a chance to test this yet, but something that did pop out at me was you are calling DrawPrimitive() with 6 as the primitive count - this should be 3, as you only want 3 lines, not 6 - which is the vertex count.

This can have really odd consequences, though i'm not sure that it is having the effects of which you speak.

dalep

331

October 21, 2005 05:48 PM

How about lighting? Is that on or off when you render these line segments? And where is the device getting its colors from? Material? Vertex?

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