forums.ps2dev.org

[Stellar]

considering sceGuStart(GU_DIRECT, disp_list); what is a display list?

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finally, i have one more question...


Im very new to psp development, so ive never used these two macros that are used everywhere in the examples. Im assuming that they're pretty important, but im not sure why?

typedef struct
{
float x,y,z;
float u, v;
unsigned int color;
} Vertex;

So what makes this

Vertex __attribute__((aligned(16))) aligned_vtx;

different from this

Vertex vertice;
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as a quick study, i did a sizeof comparison, ( wasnt sure of the sizeof's in a psp environment ).

sizeof( float ) = 4 bytes
sizeof( unsigned int ) = 4 bytes
sizeof( Vertex ) = 24 bytes
sizeof( aligned_vtx) = 24 bytes;


thx again,
sorry for the noobish questions, but we all gotta start somewhere :/
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[Drakonite]

__attribute__((aligned(16))) is used to, surprisingly enough, cause variables to be aligned on at least a certain boundry. In other words, that particular piece of code is making sure it's aligned to at least a 16byte boundry.

Why? Well, the hardware needs certain things to be aligned by certain amounts.
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Shoot Pixels Not People!
Makeshift Development

[Stellar]

thx Drakonite, i did got more detailed explanation for byte alignment here but im still drawing a blank about the psp display list?
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[ufoz]

It's just an area in memory that stores commands for the 3D hardware. When you're issuing rendering commands you're basically filling this buffer with various commands and parameters, then telling the GU to execute it all. I suppose it's actually more complicated than that but that's basically it.

[jsgf]

The interesting thing about display lists is that you can keep them around and use them over and over. So, for example, you can have a display list with all the commands to draw your main character, etc.

Lists can also call other lists too (though with a fairly shallow stack: 2 or 4 levels?).

[chp]

I would suspect at most 2 levels of stack, first from the PS2 heritage (ASR0/ASR1), and second that it wouldn't make sense to have more than 2 levels of calls. I don't have my PSP to test this with though, but it shouldn't be too hard to throw together a small test probably. :)
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GE Dominator