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POOpenGL ES 2.0 perspective projection -> cube is rectangular
 

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  1. POOpenGL ES 2.0 perspective projection -> cube is rectangular
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    <p><strong>[SOLVED - See answer in bottom]</strong></p> <p>I'm trying to draw a cube with perspective, using <em>OpenGL ES 2.0 on iOS (iPhone)</em>, but it's appearing as a rectangular shape.</p> <p>From what I've gathered searching the web it seems to be related to the viewport / projection matrix, but I can't seem to put the finger on the actual cause.</p> <p>If I set the viewport to a square measure (width == height) it draws perfectly well (a cube), but if I set it correctly (width = screen_width, height = screen_height) then the cube is drawn as a rectangular shape.</p> <p>Should setting the Projection matrix accordingly with the Viewport make the cube stay a cube?!</p> <p>My code (please let me know if more info is needed):</p> <p><strong>Render method:</strong></p> <pre><code>// viewportSize is SCREEN_WIDTH and SCREEN_HEIGHT // viewportLowerLeft is 0.0 and 0.0 ivec2 size = this-&gt;viewportSize; ivec2 lowerLeft = this-&gt;viewportLowerLeft; glViewport(lowerLeft.x, lowerLeft.y, size.x, size.y); // if I put size.x, size.x it draws well mat4 projectionMatrix = mat4::FOVFrustum(45.0, 0.1, 100.0, size.x / size.y); glUniformMatrix4fv(uniforms.Projection, 1, 0, projectionMatrix.Pointer()); </code></pre> <p><strong>Matrix operations:</strong></p> <pre><code>static Matrix4&lt;T&gt; Frustum(T left, T right, T bottom, T top, T near, T far) { T a = 2 * near / (right - left); T b = 2 * near / (top - bottom); T c = (right + left) / (right - left); T d = (top + bottom) / (top - bottom); T e = - (far + near) / (far - near); T f = -2 * far * near / (far - near); Matrix4 m; m.x.x = a; m.x.y = 0; m.x.z = 0; m.x.w = 0; m.y.x = 0; m.y.y = b; m.y.z = 0; m.y.w = 0; m.z.x = c; m.z.y = d; m.z.z = e; m.z.w = -1; m.w.x = 0; m.w.y = 0; m.w.z = f; m.w.w = 1; return m; } static Matrix4&lt;T&gt; FOVFrustum(T fieldOfView, T near, T far, T aspectRatio) { T size = near * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0); return Frustum(-size, size, -size / aspectRatio, size / aspectRatio, near, far); } </code></pre>
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    1. COWhat is the ratio in the last parameter of the FOVFrustum constructor meant to do? It seems like your issue might be there.
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    2. CO@jakev: I don't follow, how am I supposed to calculate the FOV Frustum without it? Can you elaborate on that?
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    3. COCan the order of matrix multiplication or something like that be the cause of this?
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