Hi there,
Is there a nice way of construction a mat3 from a mat4 in a vertex shader?
I see in most of the PowerVR demos this is mostly avoided by passing in the 3x3 matrix.
The glsl spec lists a number of ways including:
uniform highp mat4 c;
mat3 a©;
mat3 b(c[0].xyz,c[1].xyz,c[2].xyz);
Both of which return the rather unhelpful “syntax error: syntax error” compilation error 
The only way I seem to be able to make one, is to copy the individual vectors over.
Thanks,
Steve.
The problem you are encountering is because the syntax for the assignment differs from that which can be done in a language such as C++. Instead, you should write the following:
highp mat3 a = mat3©;
highp mat3 b = mat3(c[0].xyz,c[1].xyz,c[2].xyz);
[/CODE]
Unlike C++ syntax where (depending on the compiler) this could cause the default constructor to be called and then an assignment, the GLSL ES compiler interprets the code I’ve written above as a call to the assignment constructor.
JoeJoe2010-11-08 12:49:32<br />
<br />highp mat3 a = mat3(c);<br />
<br />highp mat3 b = mat3(c[0].xyz,c[1].xyz,c[2].xyz);<br />
<br />
Unlike C++ syntax where (depending on the compiler) this could cause the default constructor to be called and then an assignment, the GLSL ES compiler interprets the code I’ve written above as a call to the assignment constructor.
JoeJoe2010-11-08 12:49:32
