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I am deeply unhappy about the current implementation of projection transformations, particularly where parallel projections are concerned:

It seems certain that the eye coordinates to screen coordinates mapping required by parallel projection could be done more efficiently and with less potential loss of accuracy if it were hard-coded rather than set up as a general matrix transformation. In fact I am very tempted to abandon the whole idea of allowing arbitrary matrix commands (especially GL_LoadMatrix) to affect the current projection matrix. If projections could only be set up using GL_Ortho or GL_Frustum, then client programs would be protected from sticking their noses into a potentially dangerous area, and much better internal implementation would be possible.

With hindsight, I would have written the bulk of the library in C, except for a few key components such as transformations and low-level rendering functions.

This does not merely reflect a personal weariness of assembly programming. but also the fact that in recent months I have become more aware of how to help C compilers generate efficient code, whereas previously I simply blamed the compiler when I did not obtain good results: An experienced C programmer can do a lot to help register allocation, and minimise argument passing overhead and access costs to variables.

If a floating point library were available then it ought to possible to create a version of the module that does not use the FP instruction set (hence avoiding the overhead of invoking the emulator), yet uses floating point arithmetic internally. Unfortunately I do not have access to such a library, because emulation is the preferred software floating point system under RISC OS.

The performance improvement would be that the selection of hardware/software FP would be made once only, when the module was loaded, rather than on the basis of each individual instruction.

And finally, this project is self-evidently unfinished. Which is a pity, as I thought it looked quite promising.

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