From: Sengan Baring-Gould <sengan@seqnet.net>
  To  : ggi-develop@eskimo.com
  Date: Wed, 19 Aug 1998 20:54:01 -0600

Re: LibGGI3D RFC

Jon M. Taylor wrote:
>      Next is the notion of pluggable shaders.  A triangle is drawn by
> setting a bunch of pixels.  What shade those pixels are can be determined

> in a huge number of different ways.  LibGGI cannot possibly avoid bloat if
> it has to know about all those ways to shade triangles.  Therefore,
> DrawTriangle can take a pointer to a shader table entry, which contains a
> pointer to a shader function.  Thus, the code using LibGGI3D can implement
> arbitrary shaders and LibGGI3D doesn't need to know about the gory
> details.  Both prebuilt shader functions (SHADE_PHONG,
> SHADE_GORAUD_TEXURED, SHADE_FLAT, etc) and user-defined shader functions
> go in this table.  The prebuilt shaders allow DrawTriangle() to use
> hardware shading if it is present, or fall back to software shading if it
> is not.

What about texture mapping, etc. Something like Enlightenment/Gtk with
themeswould do well to use this. Also assigning gart space is definitely a GGI
kernel
level thing.

> * struct camera { float x1, y1, z1, x2, y2, z2 }. Every LibGGI3D display
> will have a camera struct attached to it.  A generic hook for arbitrary
> display data should also be present - the shaders might use it.  void
> *private_data.



> * int DrawTriangle (float x1, y1, x2, y2, x3, y3; shader_index shader; void

> *shader_data) is the core drawing function.

These lines seem to contradict: 2D triangles but 3d camera?

> Q: What about z-buffering?  You said you were going to make that part of
> the API.
>
> A: I changed my mind.  Once you start worrying about buffers, their
> dimensions, their layout, their coordinate system, etc etc you open up a
> whole can of worms.  If people want these features, they can either write
> a DirectBuffer equivalent or draw to a secondary depth buffer.  LibGGI3D
> is for drawing only.  Extra stuff should have its own API.

I disagree. Z-buffers are in the hardware: the card gets a triangle in
3spaceand draws it to 3space.

But I can see you OpenGL point. Keeping it simple is good.

Sengan