nv_point_sprite's vs. Cg Shaders

OpenGL OpenGL: Advanced Coding
1

Hi there,
i’ve been experimenting with nv_point_sprite’s and if i use “normal” mode with
-> glEnable (GL_POINT_SPRITE_NV)
-> //draw some points
-> glDisable (GL_POINT_SPRITE_NV)

everything works well. But i have to change the appearence of the sprites with my cg vertex shader and later with my fragment shader dubios things happen. The main problem here is that they have the same size, no matter what the distance of the viewer is.

Has anybody out there an idea, or experiences in programming with point sprites and shaders ??

Thank you

Schelm

2

: PSIZE ???

3

Changing the Point Size takes no effect. They stay on the same size no matter what distance they have or what the point size is.

Any ideas ??

Is there probably a demo out there using Point Sprites together with Shaders ??

Common dudes

Schelm

4

glEnable(GL_VERTEX_PROGRAM_POINT_SIZE_ARB);

should do it together with with for example following ARBvp (emulation of the ARB_point_parameters extension)

!!ARBvp1.0

vertexprogram welches die {ARB|EXT}_point_parameter extensions nachbildet

wir lassen die Festverdrahtete HW T&L pipeline die vertices transformieren.

Vertex Attribute

ATTRIB pos = vertex.position;

GL state

PARAM mv[4] = { state.matrix.modelview } ;
PARAM mvp[4] = { state.matrix.mvp};
PARAM pSize = state.point.size;
PARAM pAtt = state.point.attenuation;

Konstanten

PARAM eye= { 0.0, 0.0, 0.0, 1.0};

Hilfsvariablen

TEMP dist;
TEMP dist_sqr;
TEMP transformed;
TEMP finalsize;

#variablen initialisieren
MOV finalsize,{ 0,0,0,0 };

#vertex projezieren
DP4 result.position.x, mvp[0], pos;
DP4 result.position.y, mvp[1], pos;
DP4 result.position.z, mvp[2], pos;
DP4 result.position.w, mvp[3], pos;

vertex in eye space

DP4 transformed.x, mv[0], pos;
DP4 transformed.y, mv[1], pos;
DP4 transformed.z, mv[2], pos;
DP4 transformed.w, mv[3], pos;

abstand zu eye ( 0,0,0,1)

SUB dist_sqr, transformed, eye;
DP3 dist_sqr, dist_sqr, dist_sqr;
RSQ dist, dist_sqr.w; # dist enthält 1/d,
RCP dist, dist.w; # dist enthält d, dist.w enthält d

attenuation berechnen

pointsize = size * sqrt( 1/ ( a+ bd + cd^2))

finalsize = b * d + a

finalsize = d^2 * c + finalsize

finalsize = 1 / sqrt (finalsize )

MAD finalsize, pAtt.y, dist, pAtt.x;
MAD finalsize, pAtt.z, dist_sqr, finalsize;
RSQ finalsize.w, finalsize.w;

point size anpassen

MUL finalsize.w,pSize.x, finalsize.w;

clampen und ausgeben

MAX finalsize.w, pSize.y,finalsize.w;
MIN result.pointsize,pSize.z,finalsize.w;

farbe ausgeben

MOV result.color, vertex.color;

END

5

Thank you man,

Danke Dir

Schelm