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Can someone please help me with the following code:

gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
mat4.ortho(pMatrix, 0, gl.viewportWidth, 0, gl.viewportHeight, 0.1, 100);
mat4.identity(mvMatrix);
mat4.lookAt(mvMatrix, [0, 0, -40], [0, 0, 0], [0, 1, 0]);

Full source http://jsfiddle.net/bepa/2QXkp/

I trying to display a cube with a orthographic camera, but all I see is black. The cube should be at (0, 0, 0), the camera (0, 0, -40) and look at (0,0,0).

For all matrix transformations I use gl-matrix 2.2.0.

EDIT:

This works fine:

mat4.perspective(pMatrix, 45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0);
mat4.identity(mvMatrix);
mat4.lookAt(mvMatrix, [0, 40, -40], [0, 0, 0], [0, 1, 0]);
mat4.rotate(mvMatrix, mvMatrix, degToRad(45), [0, 1, 0]);

This don't work:

mat4.ortho(pMatrix, 0, gl.viewportWidth, 0, gl.viewportHeight, 0.1, 100);
mat4.identity(mvMatrix);
mat4.lookAt(mvMatrix, [0, 40, -40], [0, 0, 0], [0, 1, 0]);
mat4.rotate(mvMatrix, mvMatrix, degToRad(45), [0, 1, 0]);
coda
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1 Answers1

6
 mat4.ortho(pMatrix, -1.0, 1.0, -1.0, 1.0, 0.1, 100);

Gives a result that is not black ;)

The documentation of mat4.ortho():

/**
 * Generates a orthogonal projection matrix with the given bounds
 *
 * @param {mat4} out mat4 frustum matrix will be written into
 * @param {number} left Left bound of the frustum
 * @param {number} right Right bound of the frustum
 * @param {number} bottom Bottom bound of the frustum
 * @param {number} top Top bound of the frustum
 * @param {number} near Near bound of the frustum
 * @param {number} far Far bound of the frustum
 * @returns {mat4} out
 */
mat4.ortho = function (out, left, right, bottom, top, near, far) {

The width and height of the canvas is not needed for an ortho projection. But I'm not familiar enough with projection matrices to give you an in depth explanation why.

Heinzlmaen
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