OpenGL

Rotate model with GLKit – Quaternions and Matrices math

Posted on by

I was looking for algorithm to apply additional rotation to model with current rotation matrix, and found this:

1
2
3
GLKVector3 up = GLKVector3Make(0.f, 1.f, 0.f);
up = GLKQuaternionRotateVector3( GLKQuaternionInvert(quarternion), up );
GLKQuaternion quarternion = GLKQuaternionMultiply(quarternion, GLKQuaternionMakeWithAngleAndVector3Axis(delta.x * RADIANS_PER_PIXEL, up));

It’s from this small tutorial about rotation:
A bit modified code, source here
Under code a bit more text and links
Continue reading →

List of Anti-Aliasing techniques in 3D

Posted on by

I know about next Anti-Aliasing techniques:
MSAA – Multi-Sampled Anti-Aliasing
SSAA – Super-Sampled Anti-Aliasing also called FSAA
FXAA – Fast Approximate Anti-Aliasing, some good resource and this pdf
CSAA – Coverage Sample Anti-Aliasing
SMAA – Subpixel Morphological Anti-Aliasing
MLAA – Morphological Anti-Aliasing (OpenGL implementation)

If you know any other which is not in list, please write below in comment.
I will add them to list and links on page with description.

Print OpenGL error and description

Posted on by

Print OpenGL error:

1
2
3
4
GLenum err = glGetError();
if (err != GL_NO_ERROR) {
   NSLog(@"Error glGetError: glError: 0x%04X", err);
}

GL_INVALID_ENUM​, 0×0500: Given when an enumeration parameter is not a legal enumeration for that function. This is given only for local problems; if the spec allows the enumeration in certain circumstances, and other parameters or state dictate those circumstances, then GL_INVALID_OPERATION​ is the result instead.

GL_INVALID_VALUE​, 0×0501: Given when a value parameter is not a legal value for that function. This is only given for local problems; if the spec allows the value in certain circumstances, and other parameters or state dictate those circumstances, then GL_INVALID_OPERATION is the result instead.

GL_INVALID_OPERATION​, 0×0502: Given when the set of state for a command is not legal for the parameters given to that command. It is also given for commands where combinations of parameters define what the legal parameters are.

GL_OUT_OF_MEMORY​, 0×0503: Given when performing an operation that can allocate memory, but the memory cannot be allocated. The results of OpenGL functions that return this error are undefined; it is allowable for partial operations to happen.

GL_INVALID_FRAMEBUFFER_OPERATION​, 0×0506: Given when doing anything that would attempt to read from or write/render to a framebuffer that is not complete, as defined here.

GL_STACK_OVERFLOW​1, 0×0503: Given when a stack pushing operation cannot be done because it would overflow the limit of that stack’s size.

GL_STACK_UNDERFLOW​1, 0×0504: Given when a stack popping operation cannot be done because the stack is already at its lowest point.

GL_TABLE_TOO_LARGE​1, 0×8031: Part of the ARB_imaging extension.

Posted in iOS, OpenGL
Tagged error, OpenGL ES 2.0

GLKit, Opengl ES 2.0 Picking Ray for select object

Posted on by

Solution for picking

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
GLKVector4 normalisedVector = GLKVector4Make((2 * position.x / self.view.bounds.size.width - 1),
                                                 (2 * (self.view.bounds.size.height-position.y) / self.view.bounds.size.height - 1),  
                                                   -1,
                                                   1);

GLKMatrix4 inversedMatrix = GLKMatrix4Invert(_modelViewProjectionMatrix, nil);

GLKVector4 near_point = GLKMatrix4MultiplyVector4(inversedMatrix, normalisedVector);

near_point.v[3] = 1.0/near_point.v[3];
near_point = GLKVector4Make(near_point.v[0]*near_point.v[3], near_point.v[1]*near_point.v[3], near_point.v[2]*near_point.v[3], 1);

normalisedVector.z = 1.0;
GLKVector4 far_point = GLKMatrix4MultiplyVector4(inversedMatrix, normalisedVector);

far_point.v[3] = 1.0/far_point.v[3];
far_point = GLKVector4Make(far_point.v[0]*far_point.v[3], far_point.v[1]*far_point.v[3], far_point.v[2]*far_point.v[3], 1);

On

Distance between vertices and magnitude of a vector

Posted on by

Distance between vertices:

1
2
3
4
5
6
7
8
9
10
11
12
13
static inline GLfloat Vertex3DDistanceBetweenVertices
(Vertex3D vertex1, Vertex3D vertex2)
{
    GLfloat deltaX, deltaY, deltaZ;

    deltaX = vertex2.x - vertex1.x;
    deltaY = vertex2.y - vertex1.y;
    deltaZ = vertex2.z - vertex1.z;

    return sqrtf((deltaX * deltaX) +
        (deltaY * deltaY) +
        (deltaZ * deltaZ));
}

Magnitude of a vector:

1
2
3
4
5
6
static inline GLfloat Vector3DMagnitude(Vector3D vector)
{
    return sqrtf((vector.x * vector.x) +
        (vector.y * vector.y) +
        (vector.z * vector.z));
}