图形学变换中的Homogenize方法_艾孜尔江撰

Vector4 Transform::Homogenize(Vector4& result, const Vector4& vec4ToBeHomogenized)
	{
		if (vec4ToBeHomogenized.getW() == 0.f) {
			return Vector4();
		}
		float rhw = 1 / vec4ToBeHomogenized.getW();
		result.setX((1.f + vec4ToBeHomogenized.getX() * rhw) * canvasWidth * 0.5f);	// screen coordinate
		result.setY((1.f - vec4ToBeHomogenized.getY() * rhw) * canvasHeight * 0.5f); //screen coordinate ---> top down
		result.setZ(vec4ToBeHomogenized.getZ() * rhw);
		result.setW(rhw);
		return result;
	}

它的逆变换如下(逆变换主要用于求阴影时候的反求过程)：

Vector4 Transform::HomogenizeInvertion(Vector4 & result, const Vector4 & vec4ToBeInverted)
	{
		if (vec4ToBeInverted.getW() == 0.f) {
			return Vector4();
		}

		float rhw = 1.f / vec4ToBeInverted.getW();
		
		float reciprocalOfCanvasHeight = 1.f / canvasHeight;
		float reciprocalOfCanvasWidth = 1.f / canvasWidth;

		result.setX(((2 * vec4ToBeInverted.getX() * reciprocalOfCanvasWidth) - 1.f) * rhw);
		result.setY((1.f - (2 * vec4ToBeInverted.getY() * reciprocalOfCanvasHeight)) * rhw);
		result.setZ(vec4ToBeInverted.getZ() * rhw);
		result.setW(rhw);

		return result;
	}

作者：艾孜尔江·艾尔斯兰