/// <summary>
/// Use raycasting to determine the distance to the nearest wall at specified angle
/// </summary>
/// <param name="angle">angle in degrees</param>
/// <param name="objectsGrid">the grid array in which the objects are defined</param>
/// <returns>location of the first object found</returns>
private WorldObject FindObject(Angle angle, int[][] objectsGrid)
{
// Look for the nearest intersecting wall
Intersection intersection = FindIntersection(angle, objectsGrid);
if (intersection == null)
{
return null;
}
WorldObject obj = new WorldObject(intersection);
// Calculate TextureX property which determines which part of the texture to map to this object
Point gridLocation = CoordsToGrid(obj);
// Set texture for the object
obj.TextureIndex = objectsGrid[gridLocation.Y][gridLocation.X];
// Determine on which X-coordinate of the object the intersection was found
obj.TextureX = obj.IntersectsWith == IntersectionAxe.Xaxe
? (int)(obj.X % wallSize)
: (int)(obj.Y % wallSize);
return obj;
}
/// <summary>
/// Draw walls that are found for the current vertical scanline
/// </summary>
/// <param name="scanline"></param>
/// <param name="drawingBuffer"></param>
private void DrawObject(int scanline, WorldObject obj, Pixel[] drawingBuffer)
{
// Remove distortion (counter fishbowl effect)
Angle distortionRemovalAngle = new Angle(fieldOfView / 2);
distortionRemovalAngle.Turn(-angleBetweenRays.Value * (double)scanline);
obj.Distance = obj.Distance * Math.Cos(distortionRemovalAngle.ToRadians());
// Use distance to determine the size of the wall slice
int wallHeight = (int)Math.Floor(wallSize / obj.Distance * distanceToViewPort);
// The visible scale of a wall compared to its original size
double wallScale = (double)wallHeight / wallSize;
// If a wall slice is larger than the viewport height, we only need the visible section
// skipPixels indicates how many pixels from top and bottom towards the center can be skipped during rendering
int skipPixels = wallHeight > viewPort.Height ? (wallHeight - viewPort.Height) / 2 : 0;
int scanlineStartY = centerOfViewPort.Y - (wallHeight - skipPixels * 2) / 2;
// Draw wall slice (untextured)
// GLDraw.DrawLine(new Point(scanline, centerOfViewPort.Y - (wallHeight - skipPixels * 2) / 2), new Point(scanline, centerOfViewPort.Y + (wallHeight - skipPixels * 2) / 2), wall.IntersectsWith == IntersectionAxe.Xaxe ? Color.DarkGray : Color.Gray);
// Determine start indexes for texture read and viewport write buffers
int drawingBufferStart = obj.TextureX * (int)wallSize;
int viewPortBufferIndex = scanline * viewPort.Height;
// Generate a scanline with a textured wall slice
for (int y = 0 + skipPixels; y < wallHeight - skipPixels; y++)
{
// Determine index of texture pixel while taking zoom into account
int textureCurrentPixelIndex = (int)(y / wallScale);
// Current scanline pixel index
int spxIndex = y - skipPixels;
// Current viewPortBuffer index
int drawingBufferIndex = viewPortBufferIndex + spxIndex;
// Create a pixel in the scanline draw buffer
Color pixelColor = textures[obj.TextureIndex][drawingBufferStart + textureCurrentPixelIndex].Color;
if (pixelColor.ToArgb() != Color.Black.ToArgb())
{
drawingBuffer[drawingBufferIndex] = new Pixel();
drawingBuffer[drawingBufferIndex].X = scanline;
drawingBuffer[drawingBufferIndex].Y = scanlineStartY + spxIndex;
drawingBuffer[drawingBufferIndex].Color = pixelColor;
// Pixels on dark sides of walls need to be half the color value
if (obj.IntersectsWith == IntersectionAxe.Xaxe)
{
Color color = drawingBuffer[drawingBufferIndex].Color;
drawingBuffer[drawingBufferIndex].Color = Color.FromArgb(color.R / 2, color.G / 2, color.B / 2);
}
// Make walls in the distance darker
if (obj.Distance > 250)
{
double colorDivider = obj.Distance / 250;
colorDivider = (colorDivider > 3) ? 3 : colorDivider;
Color color = drawingBuffer[drawingBufferIndex].Color;
drawingBuffer[drawingBufferIndex].Color = Color.FromArgb((int)(color.R / colorDivider), (int)(color.G / colorDivider), (int)(color.B / colorDivider));
}
}
}
}
