How to find the ViewMatrix

[[GH]Rake]

In a 3d game the ViewMatrix is an array of 16 floats that defines your location in the world and your current viewport:


If you want to convert 3d coordinates into 2d coordinates in order to draw on your screen you have to find the ViewMatrix which can be difficult for beginners. I made a tutorial to show you the basic concept:

Upon finding the viewmatrix you must "transform" the coordinates by doing some matrix math outlined in this picture:


A World to Screen transformation function looks like this:

bool WorldToScreen(float * mvpmatrix, Vec3D pos, Vec3D &playerScreenCoords)
{
	//Matrix-vector Product, multiplying world(eye) coordinates by projection matrix = clipCoords
	Vec4D clipCoords;
	clipCoords.x = pos.x*mvpmatrix[0] + pos.y*mvpmatrix[4] + (pos.z)*mvpmatrix[8] + mvpmatrix[12];
	clipCoords.y = pos.x*mvpmatrix[1] + pos.y*mvpmatrix[5] + (pos.z)*mvpmatrix[9] + mvpmatrix[13];
	clipCoords.z = pos.x*mvpmatrix[2] + pos.y*mvpmatrix[6] + (pos.z)*mvpmatrix[10] + mvpmatrix[14];
	clipCoords.w = pos.x*mvpmatrix[3] + pos.y*mvpmatrix[7] + (pos.z)*mvpmatrix[11] + mvpmatrix[15];

	if (clipCoords.w < 0.1f)
		return false;

	//perspective division, dividing by clip.W = NDC
	Vec3D normalizedDeviceCoordinates;
	normalizedDeviceCoordinates.x = clipCoords.x / clipCoords.w;
	normalizedDeviceCoordinates.y = clipCoords.y / clipCoords.w;
	normalizedDeviceCoordinates.z = clipCoords.z / clipCoords.w;

	//viewport tranform to screenCooords
	playerScreenCoords.x = (windowWidth / 2 * normalizedDeviceCoordinates.x) + (normalizedDeviceCoordinates.x + windowWidth / 2);
	playerScreenCoords.y = -(windowHeight  / 2 * normalizedDeviceCoordinates.y) + (normalizedDeviceCoordinates.y + windowHeight / 2);

	return true;
}