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Migrating from LWJGL 2

Kai Burjack edited this page Dec 22, 2016 · 24 revisions

This article is for people who are currently using LWJGL 2 and wanting to switch to LWJGL 3. So if you are using LWJGL 2 and especially its "util" jar with the classes in the included vector package, you can migrate easily to JOML.

Vector and Matrix operations

JOML uses a very similar design compared to LWJGL 2's util vecmath classes, by providing instance methods writing the result back into the same object, and instance methods accepting a destination parameter. Also, methods such as rotate(), translate() and scale() post-multiply their respective transformations to the current matrix values.

One important difference is the handling of NIO FloatBuffers when getting values from or writing values into a FloatBuffer. In LWJGL 2 the position of the FloatBuffer will be incremented by load and store operations. In JOML the position will not be changed!

Some Matrix4f operations have different names or do not exist (currently) in JOML. These are listed in the following table:

LWJGL 2 JOML Alternative in JOML
setIdentity identity
setZero zero
load set
store get
loadTransposed N/A M.set(), M.transpose()
storeTransposed getTransposed
store3f get3x3

The same table for vector operations in Vector4f:

LWJGL 2 JOML Alternative in JOML
translate add
normalise normalize
load set
scale mul
store get

GLU operations

The matrix operations implemented in the GLU class are part of the Matrix4f in JOML. However, unlike the methods in LWJGL 2, JOML does not interface with OpenGL to multiply the matrices. Instead, JOML post-multiplies the projection and view transformations by the Matrix4f they are invoked on. So, they work just like the other transformation methods rotate(), scale() and translate() in JOML.

Therefore, you need to fill a FloatBuffer and use glLoadMatrixf() if you want to upload the matrix to OpenGL:

Matrix4f m = new Matrix4f();
m.perspective((float) Math.toRadians(45), (float)width/height, 0.1f, 100.0f);
FloatBuffer fb = BufferUtils.createFloatBuffer(16);
glMatrixMode(GL_PROJECTION);
glLoadMatrixf(fb.get(fb));

The following table contains the differences between LWJGL 2's GLU class and JOML's Matrix4f class:

LWJGL 2 JOML Differences
gluPerspective perspective In JOML the fov angle is given in radians
gluLookAt lookAt
gluProject project
gluUnProject unproject
gluOrtho2D ortho2D
gluPickMatrix pick
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