i am not doing near and far plane clipping here..
ok here is the sample code for software rasterization
// ChildView.h : interface of the CChildView class
//
#pragma once
enum { TOP = 0x1, BOTTOM = 0x2, RIGHT = 0x4, LEFT = 0x8 };
typedef unsigned int outcode;
// CChildView window
class CChildView : public CWnd
{
// Construction
public:
CChildView();
void ScanTriangleA(CPaintDC &dc, D3DXVECTOR3 &v1, D3DXVECTOR3 &v2, D3DXVECTOR3 &v3);
inline void CreateEdge(D3DXVECTOR3 &v1, D3DXVECTOR3 &v2, int &e1x, int &e1y, int &e2x, int &e2y);
void DrawSpansBetweenEdges( CPaintDC &dc, int e1x1, int e1y1, int e1x2, int e1y2,
int e2x1, int e2y1, int e2x2, int e2y2);
int maxLength = 0;
short longEdge = 0;
int length = 0;
// find edge with the greatest length in the y axis
// find edge with the greatest length in the y axis
for(short i = 0; i < 3; i++) {
length = ey2 - ey1;
if(length > maxLength) {
maxLength = length;
longEdge = i;
}
}
short shortEdge1 = (longEdge + 1) % 3;
short shortEdge2 = (longEdge + 2) % 3;
// draw spans between edges; the long edge can be drawn
// with the shorter edges to draw the full triangle
DrawSpansBetweenEdges(dc, ex1[longEdge], ey1[longEdge], ex2[longEdge], ey2[longEdge], ex1[shortEdge1], ey1[shortEdge1], ex2[shortEdge1], ey2[shortEdge1]);
DrawSpansBetweenEdges(dc, ex1[longEdge], ey1[longEdge], ex2[longEdge], ey2[longEdge], ex1[shortEdge2], ey1[shortEdge2], ex2[shortEdge2], ey2[shortEdge2]);
}
void CChildView::DrawSpansBetweenEdges( CPaintDC &dc, int e1x1, int e1y1, int e1x2, int e1y2,
int e2x1, int e2y1, int e2x2, int e2y2)
{
// calculate difference between the y coordinates
// of the first edge and return if 0
const int e1ydiff = e1y2 - e1y1;
if(e1ydiff == 0x0)
return;
// calculate difference between the y coordinates
// of the second edge and return if 0
const int e2ydiff = e2y2 - e2y1;
if(e2ydiff == 0x0)
return;
// calculate differences between the x coordinates
const float e1xdiff = (float)(e1x2 - e1x1);
const float e2xdiff = (float)(e2x2 - e2x1);
// calculate factors to use for interpolation
// with the edges and the step values to increase
// them by after drawing each span
const float factorStep1 = e1xdiff / e1ydiff;
const float factorStep2 = e2xdiff / e2ydiff;
// loop through the lines between the edges and draw spans
int x, xdiff, coord, iX1, iX2;
float X1 = (float)e1x1 + factorStep1 * (e2y1 - e1y1), X2 = e2x1, z;
for(int y = e2y1; y < e2y2; y++)
{
// calculate initial z-value for edges
z = ((-D)- B*y)/C;
iX1 = (int)X1;
iX2 = (int)X2;
// create and draw span
xdiff = iX2 - iX1;
if(xdiff == 0x0)
{
// increase factors
X1 = X1 + factorStep1;
X2 = X2 + factorStep2;
continue;
}
if (iX1 > iX2)
{
// draw each pixel in the span
for(x = iX2; x < iX1; x++)
{
coord = y*m_dwScreenWidth+x;
if(z >= m_fZBuffer[coord])
{
m_fZBuffer[coord] = z;
SetPixel(dc, x, y, m_dwColor);
}
z += dz;
}
}
else
{
// draw each pixel in the span
for(x = iX1; x < iX2; x++)
{
coord = y*m_dwScreenWidth+x;
if(z >= m_fZBuffer[coord])
{
m_fZBuffer[coord] = z;
SetPixel(dc, x, y, m_dwColor);
}
z += dz;
}
}
// increase factors
X1 = X1 + factorStep1;
X2 = X2 + factorStep2;
}
}
return S_OK;
}
//-----------------------------------------------------------------------------
// Name: SetupMatrices()
// Desc: Sets up the world, view, and projection transform Matrices.
//-----------------------------------------------------------------------------
VOID SetupMatrices()
{
// For our world matrix, we will just rotate the object about the y-axis.
D3DXMATRIXA16 matWorld;
D3DXMatrixIdentity( &matWorld );
g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );
// Set up our view matrix. A view matrix can be defined given an eye point,
// a point to lookat, and a direction for which way is up. Here, we set the
// eye five units back along the z-axis and up three units, look at the
// origin, and define "up" to be in the y-direction.
D3DXVECTOR3 vEyePt( 0.0f, 3.0f, -5.0f );
D3DXVECTOR3 vLookatPt( 0.0f, 0.0f, 0.0f );
D3DXVECTOR3 vUpVec( 0.0f, 0.0f, 1.0f );
D3DXMATRIXA16 matView;
D3DXMatrixLookAtLH( &matView, &vEyePt, &vLookatPt, &vUpVec );
g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView );
// For the projection matrix, we set up a perspective transform (which
// transforms geometry from 3D view space to 2D viewport space, with
// a perspective divide making objects smaller in the distance). To build
// a perpsective transform, we need the field of view (1/4 pi is common),
// the aspect ratio, and the near and far clipping planes (which define at
// what distances geometry should be no longer be rendered).
D3DXMATRIXA16 matProj;
D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI / 4, 1.0f, 1.0f, 100.0f );
g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj );
}
//-----------------------------------------------------------------------------
// Name: Render()
// Desc: Draws the scene
//-----------------------------------------------------------------------------
VOID Render()
{
// Clear the backbuffer to a black color
g_pd3dDevice->Clear( 0, NULL, D3DCLEAR_ZBUFFER | D3DCLEAR_TARGET, D3DCOLOR_XRGB( 0, 0, 0 ), 1.0f, 0 );
// Begin the scene
if( SUCCEEDED( g_pd3dDevice->BeginScene() ) )
{
// Setup the world, view, and projection Matrices
SetupMatrices();
// Present the backbuffer contents to the display
g_pd3dDevice->Present( NULL, NULL, NULL, NULL );
}
Yes Clipping has issues here and i checked it that ZBuffer has to be initialized with very low number then do the lessequal comparison but i also like to see if someone check its basic way of working whether is correct or not.
I took a quick peek in your code and I noticed that you could implement similar handling of projection and clipping as used in Direct3D and do the clipping in homogeneous space. That way your code would be closer to the Direct3D pipeline.
