The Camera - Essentials of Interactive Computer Graphics - page 371

• Approach. With the camera settings as in Tutorial 14.1, define a rectan-
gular visible volume with orthographic projection where we can control all
aspects of the volume.

Tutorial 14.2.
Project Name:
D3D _ AdjustOrtho
Library Support:
UWB_MFC_Lib1

Figure 14.9 is a screenshot of running Tutorial 14.2. Although the application
window is somewhat larger, the implementation of this tutorial is only slightly dif-
ferent from that of Tutorial 14.1. Listing 14.2 shows the set-up of the PROJECTION
matrix processor in the GrfxWindowD3D::OnPaint() function. The only differ-
ence between the implementation of this tutorial and that of Tutorial 14.1 is in
the computation of the matrix for the PROJECTION processor. The variables that
correspond to the parameters of the rectangular visible volume are controlled by
the GUI slider bars. At label A, we see the visible volume parameters being ref-
erenced for the computation of the matProj matrix, and then the matProj matrix
is loaded into the D3D PROJECTION matrix processor. As in Tutorial 14.1, we are
not interested in the details of the matProj matrix. Rather, we want to verify the
effects of changing the rectangular visible volume parameters.
We see that with the exact same camera setting as in Tutorial 14.1, the two
rectangles in the rendered image do not resemble squares in 3D space. The major
problem here is the absence of the distance hint. As humans, our visual system
expects the farther edge of the squares to be shorter than the closer ones. In the
image, those edges are of the same length. We can verify this is indeed an image
of the two squares in 3D space by raising the camera position (increasing the
value of camera y -position slider bar).

Figure 14.9. Tutorial

14.2.

void CGrfxWindowD3D::OnPaint() {
.

Source file.
GrfxWindowD3D.cpp file in
the GrfxWindow folder of the
D3D _ AdjustOrtho project.

// Identical to Tutorial 14.1
.
Step 2: initialize selected hardware and set the coordinate system parameters.
// Set WORLD and VIEW matrix processors... Identical to Tutorial 14.1
.
D3DXMATRIX matProj;
// Rect. visible volume parameters: m _ ViewWidth, m _ ViewHeight, m _ ViewNearPlane, m _ ViewFarPlane
// compute matProj
A: D3DXMatrixOrthoRH(&matProj, width/height/near/far);
// load matProj to D3D PROJECTION processor
m _ pD3DDevice->SetTransform(D3DTS _ PROJECTION, &matProj);

Listing 14.2. Details of the matrix processors settings (Tutorial 14.2).