/// <summary>
/// Writes a pixel to the buffer according to depth-test for single pass rendering.
/// </summary>
/// <param name="x">x index</param>
/// <param name="y">y index</param>
/// <param name="z">Depth buffer value</param>
/// <param name="premultColor">Premultiplied Frame buffer value</param>
/// <param name="premultTolerance">Premultiplied Tolerance buffer value</param>
public void SetPixel(int x, int y, float z, Color premultColor, Color premultTolerance)
{
if (x >= 0 && x < width && y >= 0 && y < height && z >= 0 && z <= 1.0f)
{
bool isZFightingPossible = IsPixelRendered(x, y);
bool drawPixel = DepthTest(z, zBuffer[x, y]);
if (drawPixel)
{
// Write to frame buffer according to alpha value of pixel
frameBuffer[x, y] = ColorOperations.PreMultipliedAlphaBlend(
premultColor,
frameBuffer[x, y]);
// We have a pre-multiplied tolerance value
toleranceBuffer[x, y] = ColorOperations.PreMultipliedToleranceBlend(
premultTolerance,
toleranceBuffer[x, y],
premultColor.A);
}
// See if we were within tolerance of another test result
if (isZFightingPossible)
{
if (DepthTestWithinTolerance(z, zBuffer[x, y], RenderTolerance.ZBufferTolerance))
{
// If so, ignore this pixel, since we can't be sure if it's right
toleranceBuffer[x, y] = Color.FromArgb(0, 255, 255, 255);
}
}
else if (z < RenderTolerance.NearPlaneTolerance || 1.0 - RenderTolerance.FarPlaneTolerance < z)
{
// If we're right on the near/far clipping plane, we can't be sure if this pixel is right.
// Note that the tolerance at the near plane will be considerably more than that of the
// far plane if we are using a perspective camera to view this scene.
toleranceBuffer[x, y] = Color.FromArgb(0, 255, 255, 255);
}
if (drawPixel && writeToZBuffer)
{
zBuffer[x, y] = z;
}
}
}
/// <summary>
/// Blend the contents of the RenderBuffer with a background color
/// </summary>
public void AddBackground(Color opaqueBackgroundColor)
{
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
// We keep our colors and tolerances premultiplied.
// Do the tolerance blend first so that we have the correct alpha value from the framebuffer
toleranceBuffer[x, y] = ColorOperations.PreMultipliedToleranceBlend(
toleranceBuffer[x, y],
toleranceBufferClearValue,
frameBuffer[x, y].A);
frameBuffer[x, y] = ColorOperations.PreMultipliedAlphaBlend(
frameBuffer[x, y],
opaqueBackgroundColor);
}
}
}
/// <summary>
/// Lights this pixel using precomputed lighting information.
/// </summary>
/// <param name="v">Interpolated vertex for this pixel position.</param>
protected override void ComputePixelProgram(Vertex v)
{
bool rendered = false;
Color totalTexturingTolerance = emptyColor;
for (int pass = 0; pass < textures.Length; pass++)
{
// A Filter can be null if the Material or the Brush are null.
// For those cases, we skip the material entirely.
if (textures[pass] == null)
{
continue;
}
TextureFilter currentTexture = textures[pass];
rendered = true;
// We need extra information for trilinear
if (currentTexture is TrilinearTextureFilter)
{
((TrilinearTextureFilter)currentTexture).MipMapFactor = v.MipMapFactor;
}
// Textures are not stored in premultiplied color space.
// This means that we have to wait until we find the lookup tolerance before we can premultiply
// (otherwise Alpha will be way off)
Color texel = currentTexture.FilteredTextureLookup(v.TextureCoordinates);
Color texelTolerance = emptyColor;
if (currentTexture.HasErrorEstimation)
{
texelTolerance = currentTexture.FilteredErrorLookup(
v.UVToleranceMin,
v.UVToleranceMax,
texel);
}
// Now we can premultiply.
Color premultTexel = ColorOperations.PreMultiplyColor(texel);
Color premultTexelTolerance = ColorOperations.PreMultiplyTolerance(texelTolerance, texel.A);
// Modulate precomputed lighting (which is also premultiplied) by the Brush value
Color premultColor = ColorOperations.Modulate(v.PrecomputedLight[pass], premultTexel);
Color premultTolerance = ColorOperations.Modulate(v.PrecomputedLight[pass], premultTexelTolerance);
// PrecomputedLightTolerance is NOT premultipled yet (see ComputeVertexProgram above).
// This is because we needed to know the final alpha value of lighting * texture.
//
Color premultLightTolerance = ColorOperations.PreMultiplyTolerance(v.PrecomputedLightTolerance[pass], premultColor.A);
premultTolerance = ColorOperations.Add(premultTolerance, premultLightTolerance);
// For additive materials, we need to force the alpha channel to zero.
// See notes on premultiplied blending in ColorOperations.cs
if (currentTexture.MaterialType != MaterialType.Diffuse)
{
premultColor.A = 0x00;
// Nothing needs to be done to tolerance's alpha
// because the framebuffer's alpha value will be used in the blend
}
// we need to blend
// Write to frame buffer according to alpha value of pixel
v.Color = ColorOperations.PreMultipliedAlphaBlend(premultColor, v.Color);
// Accumulate tolerance for each material pass
totalTexturingTolerance = ColorOperations.PreMultipliedToleranceBlend(
premultTolerance,
totalTexturingTolerance,
premultColor.A);
}
// Only set a pixel if we actually rendered at least one material for it ...
if (rendered)
{
// Add texturing tolerance to our existing lighting tolerance.
v.ColorTolerance = ColorOperations.Add(v.ColorTolerance, totalTexturingTolerance);
// Send the pixel to be rendered
buffer.SetPixel(
(int)Math.Floor(v.ProjectedPosition.X),
(int)Math.Floor(v.ProjectedPosition.Y),
(float)v.ProjectedPosition.Z,
v.Color,
v.ColorTolerance
);
}
}
