gistfile1.cpp

void Renderer::RenderWall(Vector2 v1, Vector2 v2, TileType::e tile, double texCoord1, double texCoord2)
{
	if (tile == TileType::None) return;

	static const double zClip = 0.2;
	static const double eps = 0.000001;

	uint tint = core->level->GetTileTint(TexType::Walls, tile);

	// Obscure walls parallel to OX 
	bool side = fabs((v2 - v1).y) >= eps;
	if (!side) 
		tint = Color::FastChannelsMul(tint, 0.7);

	// Translate input vectors into view frame
	v1 -= cameraPosition;
	v2 -= cameraPosition;

	// Rotate input vectors
	v1.Rotate(cameraRotation);
	v2.Rotate(cameraRotation);

	double x1 = v1.x;
	double z1 = v1.y;
	double x2 = v2.x;
	double z2 = v2.y;

	// Near plane clipping
	if (z1 < zClip && z2 < zClip) return;

	if (z1 < zClip) {
		double p = (zClip - z1) / (z2 - z1);
		z1 = zClip;
		x1 = x1 + (x2 - x1) * p;
		texCoord1 = texCoord1 + (texCoord2 - texCoord1) * p;
	}

	if (z2 < zClip) {
		double p = (zClip - z1) / (z2 - z1);
		z2 = zClip;
		x2 = x1 + (x2 - x1) * p;
		texCoord2 = texCoord1 + (texCoord2 - texCoord1) * p;
	}

	// Projection
	int startX = width / 2 - int(nearPlaneDistance * x1 / z1);
	int endX = width / 2 - int(nearPlaneDistance * x2 / z2);

	if (startX >= endX) return;

	int lineHeight1 = int(fabs(double(height) / z1));
	int lineHeight2 = int(fabs(double(height) / z2));

	int dx = endX - startX;

	for (int x = max(0, startX); x < min(width, endX); ++x)
	{
		double d = double(x - startX) / double(dx);
		double texModifier = 1.0 / z1 + (1.0 / z2 - 1.0 / z1) * d;

		// Depth test
		double lineDepth = z1 + d * (z2 - z1); 
		if (zBuffer[x] > lineDepth)
			zBuffer[x] = lineDepth;
		else
			continue;
			
		// Interpolate line height
		int lineHeight = int(lineHeight1 + d * (lineHeight2 - lineHeight1));

		int startY = height / 2 - lineHeight / 2 + cameraShift;
		int endY = height / 2 + lineHeight / 2 + cameraShift;

		int dy = endY - startY;

		// Interpolate tex coord
		double texCoord = (texCoord1 / z1 +  d * (texCoord2 / z2 - texCoord1 / z1)) / texModifier;

		int texX = int(texCoord * double(Consts::TileSize));

		for (int y = max(0, startY); y < min(height, endY); ++y)
		{
			int texY = int(double(y - startY) / double(dy) * double(Consts::TileSize));

			PixelShader(buffer[x + y * width], GetTexel(core->art->walls, tile, texX, texY), lineDepth, tint); 
		}
	}
}