public void RenderTriangle(Vertex v1, Vertex v2, Vertex v3, Color color, Texture texture = null)
{
// Sort by Y
if (v1.Coordinates2D.Y > v2.Coordinates2D.Y)
{
var temp = v2;
v2 = v1;
v1 = temp;
}
if (v2.Coordinates2D.Y > v3.Coordinates2D.Y)
{
var temp = v2;
v2 = v3;
v3 = temp;
}
if (v1.Coordinates2D.Y > v2.Coordinates2D.Y)
{
var temp = v2;
v2 = v1;
v1 = temp;
}
Vector3 p1 = v1.Coordinates2D;
Vector3 p2 = v2.Coordinates2D;
Vector3 p3 = v3.Coordinates2D;
var data = new ShaderData();
float NdotLight1 = light.CalcLightFraction(v1.WorldCoordinates, v1.WorldNormal);
float NdotLight2 = light.CalcLightFraction(v2.WorldCoordinates, v2.WorldNormal);
float NdotLight3 = light.CalcLightFraction(v3.WorldCoordinates, v3.WorldNormal);
float invSlope1 = 0, invSlope2 = 0;
if (p2.Y - p1.Y > 0)
{
invSlope1 = (p2.X - p1.X) / (p2.Y - p1.Y);
}
if (p3.Y - p1.Y > 0)
{
invSlope2 = (p3.X - p1.X) / (p3.Y - p1.Y);
}
// Triangle is:
// P1
// -
// --
// - -
// - -
// - - P2
// - -
// - -
// -
// P3
if (invSlope1 > invSlope2)
{
data.NdotLightV11 = NdotLight1;
data.NdotLightV12 = NdotLight3;
data.NdotLightV21 = NdotLight1;
data.NdotLightV22 = NdotLight2;
data.TextureU11 = v1.TextureCoordinates.X;
data.TextureU12 = v3.TextureCoordinates.X;
data.TextureU21 = v1.TextureCoordinates.X;
data.TextureU22 = v2.TextureCoordinates.X;
data.TextureV11 = v1.TextureCoordinates.Y;
data.TextureV12 = v3.TextureCoordinates.Y;
data.TextureV21 = v1.TextureCoordinates.Y;
data.TextureV22 = v2.TextureCoordinates.Y;
for (int currY = (int)p1.Y; currY < (int)p2.Y; currY++)
{
data.CurrentY = currY;
ProcessShaders(data, v1, v3, v1, v2, color, texture);
}
data.NdotLightV11 = NdotLight1;
data.NdotLightV12 = NdotLight3;
data.NdotLightV21 = NdotLight2;
data.NdotLightV22 = NdotLight3;
data.TextureU11 = v1.TextureCoordinates.X;
data.TextureU12 = v3.TextureCoordinates.X;
data.TextureU21 = v2.TextureCoordinates.X;
data.TextureU22 = v3.TextureCoordinates.X;
data.TextureV11 = v1.TextureCoordinates.Y;
data.TextureV12 = v3.TextureCoordinates.Y;
data.TextureV21 = v2.TextureCoordinates.Y;
data.TextureV22 = v3.TextureCoordinates.Y;
for (int currY = (int)p2.Y; currY <= (int)p3.Y; currY++)
{
data.CurrentY = currY;
ProcessShaders(data, v1, v3, v2, v3, color, texture);
}
}
// Triangle is:
// P1
// -
// --
// - -
// - -
// P2 - -
// - -
// - -
// -
// P3
else
{
data.NdotLightV11 = NdotLight1;
data.NdotLightV12 = NdotLight2;
data.NdotLightV21 = NdotLight1;
data.NdotLightV22 = NdotLight3;
data.TextureU11 = v1.TextureCoordinates.X;
data.TextureU12 = v2.TextureCoordinates.X;
data.TextureU21 = v1.TextureCoordinates.X;
data.TextureU22 = v3.TextureCoordinates.X;
data.TextureV11 = v1.TextureCoordinates.Y;
data.TextureV12 = v2.TextureCoordinates.Y;
data.TextureV21 = v1.TextureCoordinates.Y;
data.TextureV22 = v3.TextureCoordinates.Y;
for (int currY = (int)p1.Y; currY <= (int)p2.Y; currY++)
{
data.CurrentY = currY;
ProcessShaders(data, v1, v2, v1, v3, color, texture);
}
data.NdotLightV11 = NdotLight2;
data.NdotLightV12 = NdotLight3;
data.NdotLightV21 = NdotLight1;
data.NdotLightV22 = NdotLight3;
data.TextureU11 = v2.TextureCoordinates.X;
data.TextureU12 = v3.TextureCoordinates.X;
data.TextureU21 = v1.TextureCoordinates.X;
data.TextureU22 = v3.TextureCoordinates.X;
data.TextureV11 = v2.TextureCoordinates.Y;
data.TextureV12 = v3.TextureCoordinates.Y;
data.TextureV21 = v1.TextureCoordinates.Y;
data.TextureV22 = v3.TextureCoordinates.Y;
for (int currY = (int)p2.Y; currY <= (int)p3.Y; currY++)
{
data.CurrentY = currY;
ProcessShaders(data, v2, v3, v1, v3, color, texture);
}
}
}
private void ProcessShaders(ShaderData data, Vertex v11, Vertex v12, Vertex v21, Vertex v22, Color color, Texture texture)
{
int currY = data.CurrentY;
Vector3 p11 = v11.Coordinates2D;
Vector3 p12 = v12.Coordinates2D;
Vector3 p21 = v21.Coordinates2D;
Vector3 p22 = v22.Coordinates2D;
// Gradient is max if two vertices are on the same Y.
var leftGradient = p11.Y == p12.Y ? 1 : (currY - p11.Y) / (p12.Y - p11.Y);
var rightGradient = p21.Y == p22.Y ? 1 : (currY - p21.Y) / (p22.Y - p21.Y);
// Interpolating on Y
int leftX = (int)MathEx.Interpolate(p11.X, p12.X, leftGradient);
int rightX = (int)MathEx.Interpolate(p21.X, p22.X, rightGradient);
float leftZ = MathEx.Interpolate(p11.Z, p12.Z, leftGradient);
float rightZ = MathEx.Interpolate(p21.Z, p22.Z, rightGradient);
float leftNdotLight = MathEx.Interpolate(data.NdotLightV11, data.NdotLightV12, leftGradient);
float rightNdotLight = MathEx.Interpolate(data.NdotLightV21, data.NdotLightV22, rightGradient);
var leftU = MathEx.Interpolate(data.TextureU11, data.TextureU12, leftGradient);
var rightU = MathEx.Interpolate(data.TextureU21, data.TextureU22, rightGradient);
var leftV = MathEx.Interpolate(data.TextureV11, data.TextureV12, leftGradient);
var rightV = MathEx.Interpolate(data.TextureV21, data.TextureV22, rightGradient);
for (var currX = leftX; currX < rightX; currX++)
{
// Interpolating on X
float gradient = (currX - leftX) / (float)(rightX - leftX);
var currZ = MathEx.Interpolate(leftZ, rightZ, gradient);
var currNdotLight = MathEx.Interpolate(leftNdotLight, rightNdotLight, gradient);
var currU = MathEx.Interpolate(leftU, rightU, gradient);
var currV = MathEx.Interpolate(leftV, rightV, gradient);
var currColor = CalcColor(color, currNdotLight, texture, currU, currV);
PutPixel(currX, currY, currZ, currColor);
}
}