void DrawScanline(HScanline scanline)
{
HScreenDevice ScreenDevice = HScreenDevice.GetInstance();
List <byte> framebuffer = ScreenDevice.FrameBuff;
List <float> zbuffer = ScreenDevice.DepthBuff;
int x = (int)scanline.x;
int y = (int)scanline.y;
int scanlineWidth = (int)scanline.width;
int ScreenWidth = ScreenDevice.ScreenWidth;
int ScreenHeight = ScreenDevice.ScreenHeight;
for (; scanlineWidth > 0; x++, scanlineWidth--)
{
if (x >= 0 && x < ScreenWidth)
{
float rhw = scanline.v.rhw;
if (rhw >= zbuffer[x + y * ScreenWidth])
{
float w = 1.0f / rhw;
zbuffer[x + y * ScreenWidth] = rhw;
float u = scanline.v.uv.u * w;
float v = scanline.v.uv.v * w;
v2f fragIn = new v2f();
fragIn.uv.u = u;
fragIn.uv.v = v;
int color = frag(fragIn); //片元着色器
byte r = (byte)0x0, g = (byte)0x0, b = (byte)0x0, a = (byte)0x0;
MathHelper.GetRGBAFromInt(color, ref r, ref g, ref b, ref a);
framebuffer[(x + y * ScreenWidth) * 4] = r;
framebuffer[(x + y * ScreenWidth) * 4 + 1] = g;
framebuffer[(x + y * ScreenWidth) * 4 + 2] = b;
framebuffer[(x + y * ScreenWidth) * 4 + 3] = a;
}
}
scanline.v = scanline.v.Add(scanline.step);
if (x >= ScreenWidth)
{
break;
}
}
}
// 主渲染函数
void DrawTrap(HTrapezoid trap)
{
//HScanline scanline;
int j, top, bottom;
top = (int)(trap.top + 0.5f);
bottom = (int)(trap.bottom + 0.5f);
for (j = top; j < bottom; j++)
{
if (j >= 0 && j < HScreenDevice.GetInstance().ScreenHeight) //todo
//插值得到梯形的腰的两个点
{
trap.EdgeInterp((float)j + 0.5f);
//初始化扫描线
HScanline scanline = GetScanline(trap, j);
//绘制扫描线
DrawScanline(scanline);
}
}
}
// 根据左右两边的端点，初始化计算出扫描线的起点和步长
HScanline GetScanline(HTrapezoid trap, int y)
{
HScanline scanlineRet = new HScanline();
// 左右两点的 宽度
float width = trap.right.v.pos.x - trap.left.v.pos.x;
// 起点X 坐标
scanlineRet.x = (int)(trap.left.v.pos.x + 0.5f);
// 宽度
scanlineRet.width = (int)(trap.right.v.pos.x + 0.5f) - scanlineRet.x;
// y坐标
scanlineRet.y = y;
// 扫描起点
scanlineRet.v = trap.left.v.Copy();
//
if (trap.left.v.pos.x >= trap.right.v.pos.x)
{
scanlineRet.width = 0;
}
//计算步伐
scanlineRet.step = trap.left.v.Step(trap.right.v, width);
return(scanlineRet);
}