public void DrawTriangle(T2DTriangle Triangle)
{
Point ScreenPoint1 = new Point(Triangle.Corner1.X + HalfWidth, HalfHeight - Triangle.Corner1.Y);
Point ScreenPoint2 = new Point(Triangle.Corner2.X + HalfWidth, HalfHeight - Triangle.Corner2.Y);
Point ScreenPoint3 = new Point(Triangle.Corner3.X + HalfWidth, HalfHeight - Triangle.Corner3.Y);
VScreenCanvas.DrawLine(PenForWireFrame, ScreenPoint1, ScreenPoint2);
VScreenCanvas.DrawLine(PenForWireFrame, ScreenPoint2, ScreenPoint3);
VScreenCanvas.DrawLine(PenForWireFrame, ScreenPoint3, ScreenPoint1);
}
// Draw a filled triangle on a given rendering context
public static void DrawFilledTriangle(T2DTriangle Triangle, CRenderContext Context, Color FillColor, float M, float N, float K)
{
// Scan the list to find the top and bottom of the polygon
int MinIndexL = 0;
int MaxIndex = 0;
int MinPoint_Y = Triangle.Corner1.Y;
int MaxPoint_Y = MinPoint_Y;
int CurrentIndex, PreviousIndex;
// Create a temporary array for triangle corner points
Point[] Points = new Point[3] {
Triangle.Corner1, Triangle.Corner2, Triangle.Corner3
};
for (int i = 1; i < 3; i++)
{
if (Points[i].Y < MinPoint_Y)
{
// new top
MinPoint_Y = Points[i].Y;
MinIndexL = i;
}
else
if (Points[i].Y > MaxPoint_Y)
{
// new bottom
MaxPoint_Y = Points[i].Y;
MaxIndex = i;
}
}
if (MinPoint_Y == MaxPoint_Y)
{
// Triangle is 0-height
return;
}
// Scan in ascending order to find the last top-edge point
int MinIndexR = MinIndexL;
while (Points[MinIndexR].Y == MinPoint_Y)
{
MinIndexR = IndexForward(MinIndexR);
}
// back up to last top-edge point
MinIndexR = IndexBackward(MinIndexR);
// Now scan in descending order to find the first top-edge point
while (Points[MinIndexL].Y == MinPoint_Y)
{
MinIndexL = IndexBackward(MinIndexL);
}
// back up to first top-edge point
MinIndexL = IndexForward(MinIndexL);
// Figure out which direction through the vertex list from the top
// vertex is the left edge and which is the right}
int LeftEdgeDir = -1; // {assume left edge runs down thru vertex list
int TopIsFlat;
if (Points[MinIndexL].X != Points[MinIndexR].X)
{
TopIsFlat = 1;
}
else
{
TopIsFlat = 0;
}
// If the top is flat, just see which of the ends is leftmost
if (TopIsFlat == 1)
{
if (Points[MinIndexL].X > Points[MinIndexR].X)
{
LeftEdgeDir = 1; // left edge runs up through vertex list
int Temp = MinIndexL; // swap the indices so MinIndexL
MinIndexL = MinIndexR; //points to the start of the left
MinIndexR = Temp; // edge, similarly for MinIndexR
}
}
else
{
// Point to the downward end of the first line of each of the
// two edges down from the top}
int NextIndex = MinIndexR;
NextIndex = IndexForward(NextIndex);
PreviousIndex = MinIndexL;
PreviousIndex = IndexBackward(PreviousIndex);
// Calculate X and Y lengths from the top vertex to the end of
// the first line down each edge; use those to compare slopes
// and see which line is leftmost
int DeltaXN = Points[NextIndex].X - Points[MinIndexL].X;
int DeltaYN = Points[NextIndex].Y - Points[MinIndexL].Y;
int DeltaXP = Points[PreviousIndex].X - Points[MinIndexL].X;
int DeltaYP = Points[PreviousIndex].Y - Points[MinIndexL].Y;
if ((DeltaXN * DeltaYP - DeltaYN * DeltaXP) < 0)
{
LeftEdgeDir = 1; // left edge runs up through vertex list
int Temp = MinIndexL; // swap the indices so MinIndexL
MinIndexL = MinIndexR; // points to the start of the left
MinIndexR = Temp; // edge, similarly for MinIndexR
}
}
// Set the # of scan lines in the polygon, skipping the bottom edge
// and also skipping the top vertex if the top isn't flat because
// in that case the top vertex has a right edge component, and set
// the top scan line to draw, which is likewise the second line of
// the polygon unless the top is flat}
int HLineListLength = MaxPoint_Y - MinPoint_Y - 1 + TopIsFlat;
if (HLineListLength <= 0)
{
// there's nothing to draw, so we're done
return;
}
THLine[] HLineList = new THLine[HLineListLength];
int HLineListYStart = MinPoint_Y + 1 - TopIsFlat;
// Scan the left edge and store the boundary points in the list
// Initial pointer for storing scan converted left-edge coords
int EdgePointPtr = 0;
// Start from the top of the left edge
CurrentIndex = MinIndexL;
PreviousIndex = MinIndexL;
// Skip the first point of the first line unless the top is flat;
// if the top isn't flat, the top vertex is exactly on a right
// edge and isn't drawn}
int SkipFirst = 1 - TopIsFlat;
// Scan convert each line in the left edge from top to bottom
do
{
CurrentIndex = IndexMove(CurrentIndex, LeftEdgeDir, 3);
ScanEdge(Points[PreviousIndex].X, Points[PreviousIndex].Y,
Points[CurrentIndex].X, Points[CurrentIndex].Y, 1,
SkipFirst, ref EdgePointPtr, HLineList, Context.HalfHeight);
PreviousIndex = CurrentIndex;
SkipFirst = 0; // scan convert the first point from now on
} while(CurrentIndex != MaxIndex);
// Scan the right edge and store the boundary points in the list
EdgePointPtr = 0;
CurrentIndex = MinIndexR;
PreviousIndex = MinIndexR;
SkipFirst = 1 - TopIsFlat;
// Scan convert the right edge, top to bottom. X coordinates are
// adjusted 1 to the left, effectively causing scan conversion of
// the nearest points to the left of but not exactly on the edge}
do
{
CurrentIndex = IndexMove(CurrentIndex, -LeftEdgeDir, 3);
ScanEdge(Points[PreviousIndex].X - 1, Points[PreviousIndex].Y,
Points[CurrentIndex].X - 1, Points[CurrentIndex].Y, 0,
SkipFirst, ref EdgePointPtr, HLineList, Context.HalfHeight);
PreviousIndex = CurrentIndex;
SkipFirst = 0; // scan convert the first point from now on
} while(CurrentIndex != MaxIndex);
// {Draw the line list representing the scan converted polygon}
DrawHorizontalLineList(Context, HLineList, HLineListYStart, FillColor.ToArgb(), M, N, K);
}
// Perform rendering on a specific context
public void Render(CRenderContext Context)
{
if (!Visible)
{
return;
}
// Calculate transform matrix
TMat4x4 Mat = GetTransformMatrix(Context);
// Calculate the inverse matrix
TMat4x4 InverseMat = Mat.FindInverseMat();
// Clear translation effect
InverseMat.ClearTranslation();
// Calculate the viewer position in object coordinates
TVertex ViewDirection = Context.GetViewDirection();
TVertex ViewerPosInObjCoords = InverseMat.MulVertex(ViewDirection);
float PerspectiveFactor = Context.GetPerspectiveFactor();
Color IlluminatedFaceColor;
foreach (TFace3D Face in FaceTable)
{
bool FaceVisible;
float FaceDotProd = 0;
if (!Context.IsBackfaceCullingMode())
{
// No backface culling, the face is always visible
FaceVisible = true;
}
else
{
// Do backface culling
FaceDotProd = Math3D.DotProduct(ViewerPosInObjCoords, Face.Normal);
// Perspective mode
if (Context.IsPerspectiveMode())
{
// Remember if the face is visible
FaceVisible = (FaceDotProd > THRESHOLD_FOR_CULLING);
}
else
{
FaceVisible = (FaceDotProd > 0);
}
}
if (FaceVisible)
{
// Get current face vertices and transform to world coordinates
TVertex[] FaceVertex = new TVertex[3] {
Mat.MulVertex(VertexTable[Face.AIndex]),
Mat.MulVertex(VertexTable[Face.BIndex]),
Mat.MulVertex(VertexTable[Face.CIndex])
};
Point[] ScreenCoords = new Point[3];
if (TestForBackClipping(FaceVertex[0], FaceVertex[1], FaceVertex[2]))
{
bool PreventFaceDraw = false;
// Perspective mode
if (Context.IsPerspectiveMode())
{
// Transform the from world coordinates to screen coordinates
for (int i = 0; i < 3; i++)
{
if (Math.Abs(FaceVertex[i].Z) < POLYGON_Z_MIN_VALUE)
{
PreventFaceDraw = true;
break;
}
ScreenCoords[i].X = (int)(FaceVertex[i].X * PerspectiveFactor / FaceVertex[i].Z);
ScreenCoords[i].Y = (int)(FaceVertex[i].Y * PerspectiveFactor / FaceVertex[i].Z);
if ((Math.Abs(ScreenCoords[i].X) > POLYGON_COORD_MAX_VALUE) || (Math.Abs(ScreenCoords[i].Y) > POLYGON_COORD_MAX_VALUE))
{
PreventFaceDraw = true;
break;
}
}
}
else
// Orthogonal projection
{
PreventFaceDraw = false;
// Transform the from world coordinates to screen coordinates
for (int i = 0; i < 3; i++)
{
ScreenCoords[i].X = (int)(FaceVertex[i].X / ORTHO_PROJECTION_SCALING);
ScreenCoords[i].Y = (int)(FaceVertex[i].Y / ORTHO_PROJECTION_SCALING);
}
}
if (!PreventFaceDraw)
{
T2DTriangle ScreenTriangle = new T2DTriangle(ScreenCoords[0], ScreenCoords[1], ScreenCoords[2]);
if (Context.IsWireFrameMode())
{
Context.DrawTriangle(ScreenTriangle);
}
else
// Filled triangles mode
{
float LightLevel = FaceDotProd + MIN_LIGHT_LEVEL;
// Clip to maximum light level
if (LightLevel > 1.0)
{
LightLevel = 1.0f;
}
// Calculate face color
int ARGBColor = ClipColorChn(Face.Color.R, LightLevel);
ARGBColor |= ClipColorChn(Face.Color.G, LightLevel) << 8;
ARGBColor |= ClipColorChn(Face.Color.B, LightLevel) << 16;
// Set maximum alpha channel value
ARGBColor = (int)((uint)ARGBColor | 0xff000000);
IlluminatedFaceColor = Color.FromArgb(ARGBColor);
// Calculate factors for the polygon filling routine
TVertex FaceNormal = Math3D.CalcFaceNormal(FaceVertex[0], FaceVertex[1], FaceVertex[2]);
float M, N, K;
CalculatePolygonFactors(FaceNormal, FaceVertex[1], PerspectiveFactor, out M, out N, out K);
TriangleFiller.DrawFilledTriangle(ScreenTriangle, Context, IlluminatedFaceColor, M, N, K);
}
}
}
}
}
RenderChildObjects(Context);
}