bool RenderPrimitive(UInt16 address, PrimitiveInstruction opCode)
{
float shade = 0;
// check if first vertex is a normal vector
VertexInstruction vertex = Memory[address];
if (vertex.IsNormalVector)
{
// get the normal vector
Vector3 normal = GetVertexFromTable(vertex);
normal = Vector3.Transform(normal, Parent.WorldRotation);
// get the first coordinate
Vector3 pt = GetVertexFromTable(Memory[address + 1]);
pt = Vector3.Transform(pt, Parent.D3DTS_WORLD);
// check if surface is visible
if (Vector3.Dot(normal, pt) <= 0)
{
return(false); // not visible
}
// if shading enabled
if (opCode.IsShaded)
{
// both values are 14 bit fractional precision
// so dot product must be dividied by 2^(14+14) to normalize from 0.0 - 1.0
// but then we multiply by 8 (2^3) to convert to a pallete index
// so we divide by 2^(14+14-3)
const float scale = 1.0f / (1 << 25);
shade = Vector3.Dot(normal, Parent.Light) * scale;
shade = Math.Min(7, Math.Max(0, shade));
}
}
// should we skip rendering?
if (opCode.SkipRender)
{
return(true); // would have been visible
}
// prepare the vertex buffer
BuildPrimitive(address, Parent.GetColor(opCode.ColorIndex, shade), opCode.RenderMode);
return(true);
}
void BuildPrimitive(UInt16 address, Color color, Mathbox.RenderMode renderMode)
{
// add points to buffer
for (int numVertices = 0; ;)
{
VertexInstruction vertex = Memory[++address];
Vertices[numVertices++] = Vector3.Transform(GetVertexFromTable(vertex), Parent.D3DTS_WORLD);
// is this the last point of the plygon?
if (vertex.IsLastVertex)
{
#if DEBUG
if (MaxVertices < numVertices)
{
MaxVertices = numVertices;
Debug.WriteLine($"Max Vertices = {MaxVertices}");
}
#endif
DisplayListManager.AddPrimitive(renderMode, Vertices, numVertices, color);
return;
}
}
}
Vector3 GetVertexFromTable(VertexInstruction vertex)
{
return(Parent.GetVectorAt((UInt16)(VertexTableAddr + vertex.VertexOffset)));
}