All,
Recall that I am (re)developing a multiple turtle, turtle graphics system
using modern openGL. I have been unable to find examples of how to do this,
and the examples that come close use C++ and GLM which hide from me some of
the essentials. What follows is my current understanding of how I might
proceed. I want advice, please.
Consider the "model-view" line (just below) for transformations in
shader.ijs. (The "Projection" line immediately after the "model-view" line
in the code is not relevant to my comments.)
NB. model-view (*********line wrap is bad here********)
mvp=: (gl_Rotate (0{R), 1 0 0 ) mp (gl_Rotate (1{R), 0 1 0) mp (gl_Rotate
(2{R), 0 0 1) mp (gl_Scale STEPS%100) mp (gl_Translate 0 0 _8) mp
glu_LookAt EYE,LR,UD,IO,UP
But I do not think that "model-view" line can be used effectively in a
turtleS (plural) graphical system because the calculation is really moving
the system camera (I call it the Eye) so it can focus on a specific target
in the scene.
I believe, but want to proved wrong, that instead each turtle has to have
its own vertexData array and that array must be rewritten after each
position or heading change. It is possible that only turtles that do so
move require a change of their vertices and position. Furthermore, a
separate current heading matrix and gl_Position for each turtle must be
computed and stored after each rotation and translation, respectively.
I may be wrong about gl_Position above, because that special value may be
associated with the camera and not with the individual objects. Does anyone
know about that?
If I am correct that each turtle's moving or turning vertices have to be
altered, I believe I understand how gl_Rotate and gl_Translate can be
applied to vertices to generate knew vertices, and how a new 3x3 heading
array can be computed after each rotation and how revised position vectors
can be computed. Saving the heading array and the position vectors may be
more efficient in j than in openGL, but I have not thought that through.
It seems to me that it might be very desirable to save the revised
vertexData vertices in their original location so that the pointer in
"symdat <'vertexData'" can be used without rebinding the vector buffer. But
I have no idea if or how that might be done. Help, please.
Any help on these issues would be greatly appreciated.
--
(B=)
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