Re: [AD] depth buffer API

[Peter Wang <novalazy@xxxxxxxxxx>]

On Sun, 6 May 2012 00:54:04 +0200, Elias Pschernig <elias.pschernig@xxxxxxxxxx> wrote:
> Too lazy to search for previous discussions about this, but would the
> following API addition make sense?
> 
> /* Clears the depth buffer to the specified value. */
> 
> void al_clear_depth_buffer(float x);
> 
> void al_set_depth_buffer(
> 	ALLEGRO_DEPTHFUNC function,
> 	ALLEGRO_DEPTH_BUFFER_FLAGS flags);
> 
> /* Determines how the depth value of new pixels is compared to
> existing depth values in the depth buffer. */
> 
> enum ALLEGRO_DEPTHFUNC {
> 	ALLEGRO_DEPTHFUNC_NEVER,
>         ALLEGRO_DEPTHFUNC_ALWAYS,
> 	ALLEGRO_DEPTHFUNC_LESS, 
> 	ALLEGRO_DEPTHFUNC_EQUAL,     
> 	ALLEGRO_DEPTHFUNC_LESS_EQUAL,       
> 	ALLEGRO_DEPTHFUNC_GREATER,        
> 	ALLEGRO_DEPTHFUNC_NOT_EQUAL, 
> 	ALLEGRO_DEPTHFUNC_GREATER_EQUAL};
> 
> enum ALLEGRO_DEPTH_BUFFER_FLAGS {
> 
> 	/* If this flag is not set no depth testing is done. */
> 
>         ALLEGRO_DEPTH_CHECK = 1,

I suggest ALLEGRO_DEPTH_TEST.

> 
> 	/* If this flag is not set the depth buffer is not updated. */
> 
> 	ALLEGRO_DEPTH_WRITE = 2,
> 
> 	/* If this flag is set the color buffer is not updated. */
> 
> 	ALLEGRO_NO_COLOR_WRITE = 4};

Not another NO flag.  But I don't think this belongs with the depth
buffer API.

Is the only way to make use of the depth buffer from pure Allegro code
the primitives addon?  I guess we would need to document the z values
for al_draw_bitmap, etc. and the font addons.

Since the depth buffer state is per target bitmap, al_set_depth_buffer
would just fail for memory bitmaps (except when the arguments are
trivial)?

Peter