void OcclusionBuffer::DrawTriangle(Vector4* vertices)
{
unsigned clipMask = 0;
unsigned andClipMask = 0;
bool drawOk = false;
Vector3 projected[3];
// Build the clip plane mask for the triangle
for (unsigned i = 0; i < 3; ++i)
{
unsigned vertexClipMask = 0;
if (vertices[i].x_ > vertices[i].w_)
vertexClipMask |= CLIPMASK_X_POS;
if (vertices[i].x_ < -vertices[i].w_)
vertexClipMask |= CLIPMASK_X_NEG;
if (vertices[i].y_ > vertices[i].w_)
vertexClipMask |= CLIPMASK_Y_POS;
if (vertices[i].y_ < -vertices[i].w_)
vertexClipMask |= CLIPMASK_Y_NEG;
if (vertices[i].z_ > vertices[i].w_)
vertexClipMask |= CLIPMASK_Z_POS;
if (vertices[i].z_ < 0.0f)
vertexClipMask |= CLIPMASK_Z_NEG;
clipMask |= vertexClipMask;
if (!i)
andClipMask = vertexClipMask;
else
andClipMask &= vertexClipMask;
}
// If triangle is fully behind any clip plane, can reject quickly
if (andClipMask)
return;
// Check if triangle is fully inside
if (!clipMask)
{
projected[0] = ViewportTransform(vertices[0]);
projected[1] = ViewportTransform(vertices[1]);
projected[2] = ViewportTransform(vertices[2]);
if (CheckFacing(projected[0], projected[1], projected[2]))
{
DrawTriangle2D(projected);
drawOk = true;
}
}
else
{
bool triangles[64];
// Initial triangle
triangles[0] = true;
unsigned numTriangles = 1;
if (clipMask & CLIPMASK_X_POS)
ClipVertices(Vector4(-1.0f, 0.0f, 0.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_X_NEG)
ClipVertices(Vector4(1.0f, 0.0f, 0.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_Y_POS)
ClipVertices(Vector4(0.0f, -1.0f, 0.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_Y_NEG)
ClipVertices(Vector4(0.0f, 1.0f, 0.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_Z_POS)
ClipVertices(Vector4(0.0f, 0.0f, -1.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_Z_NEG)
ClipVertices(Vector4(0.0f, 0.0f, 1.0f, 0.0f), vertices, triangles, numTriangles);
// Draw each accepted triangle
for (unsigned i = 0; i < numTriangles; ++i)
{
if (triangles[i])
{
unsigned index = i * 3;
projected[0] = ViewportTransform(vertices[index]);
projected[1] = ViewportTransform(vertices[index + 1]);
projected[2] = ViewportTransform(vertices[index + 2]);
if (CheckFacing(projected[0], projected[1], projected[2]))
{
DrawTriangle2D(projected);
drawOk = true;
}
}
}
}
if (drawOk)
++numTriangles_;
}
void iGraphics::draw_triangle (int x1, int y1, int x2, int y2, int x3, int y3)
{
DrawTriangle2D (x1, invert (y1), x2, invert (y2), x3, invert (y3));
};
