Look at?

[Orkin]

Can anyone help me out with the gSPLookAtX and gSPLookAtY commands? I thought I had it figured out, but now I'm not so sure.

At first I thought they were used to specify vectors (through the Light structure) that define a new coordinate system, that could then be used to build a matrix to transform the vertex normals thereby manipulating them to control the texture coordinate generation. But sometimes the ROMs are sending values like {x=0, y=0, z=0}, which isn't a valid vector...and some games are even using the color and pad values in the Light structure!?

I'm very confused by this...all I can figure out is that some ucodes are trying to do something completely different from what is described in the documentation (which is very vague anyway).

Thanks in advance for any info you can provide!

Orkin

 

[Hacktarux]

That's the only info i have about this command, maybe you already have it as i've found it in the patent:

This command is used for automatic texture coordinate generation. It is used to describe the orientation of the eye so that the signal processor 400 knows with respect to what to generate texture coordinates. The XYZ values (8 bit signed fractions with 7 bits of fraction) describe a vector in worldspace (the space between the MODELUIEW matrix and the PROJECTION matrix) which is perpendicular to the
viewer's viewing direction and pointing towards the viewer's right.

 

[olivieryuyu]

quite unsure it 'll help:


GBI Commands
gSPLookAt, gSPLookAtX, and gSPLookAtY - Load the 'lookat' structure to the RSP for specular highlights or reflection mapping.