CODEWITHSUNDEEP
javaopengl
user3385594
user3385594

Reputation: 23

Why is this code passing in the size in BITS to opengl's glBufferData method instead of bytes (java)

According to the opengl documentation when you call glBufferData the size parameter needs to be in bytes.

However this is a snippet from a program (that works perfectly fine) 

long vertBsize = ((short)5) * 4l * 4l; 
glBindBuffer ( GL.GL_ARRAY_BUFFER, vbuffer);
glBufferData ( GL.GL_ARRAY_BUFFER, vertBsize , points, GL.GL_STATIC_DRAW);

According to the java documentation a short is 16-bits so in my mind this code snippet is incorrectly sending the number of BITS in the points buffer.

Am I stupid/way too tired or am I missing something

Upvotes: 0

Views: 35

Answers (1)

user3385594
user3385594

Reputation: 23

@Reto Koradi's - question for more detail ultimately led me to the answer.

The points buffer contains all floats. The floats are split into sets of four:

{1.0,2.0,4.0,1.0,
 2.0,3.0,8.0,1.0,
 3.0,4.0,2.0,1.0,
 2.0,3.0,8.0,1.0,
 1.0,2.0,4.0,1.0}

Since a float == 32 bits == 4bytes. The formula 5(sets of floats)* 4(floats per set) * 4(bytes of data per float) does indeed come out to the correct amount of bytes.

Upvotes: 1

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