Mesa 3D声称通过osmesa32支持32条浮动点色道。 问题在于,浮点号被装入8轨! 是否有任何人注意到这一点? 下面是用于测试的短程Im。 您将看到我起草一份带有特定浮点颜色的平面图(全方位观点),然后读到第一页的颜色:

#include <stdio.h>
#include <stdlib.h>
#include "GL/osmesa.h"
#include "GL/glut.h"

#define WIDTH 100
#define HEIGHT 100

void draw()
{
GLint r, g, b, a;
glGetIntegerv(GL_RED_BITS, &r);
glGetIntegerv(GL_GREEN_BITS, &g);
glGetIntegerv(GL_BLUE_BITS, &b);
glGetIntegerv(GL_ALPHA_BITS, &a);
printf("channel sizes: %d %d %d %d
", r, g, b, a);

glEnable(GL_DEPTH_TEST);


glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glTranslatef(0.0, 0.0, -1.0); 

// draw a plane
glBegin(GL_QUADS);
glColor3f(0.5f, 0.56789f, 0.568f);
glVertex3f(-1, -1, 0);
glVertex3f(-1, 1, 0);
glVertex3f(1, 1, 0);
glVertex3f(1, -1, 0);
glEnd();

glFinish();
}

int main( int argc, char *argv[] )
{
GLfloat *buffer;

/* Create an RGBA-mode context */
#if OSMESA_MAJOR_VERSION * 100 + OSMESA_MINOR_VERSION >= 305
/* specify Z, stencil, accum sizes */
OSMesaContext ctx = OSMesaCreateContextExt( GL_RGB, 16, 0, 0, NULL );
#else
OSMesaContext ctx = OSMesaCreateContext( GL_RGB, NULL );
#endif
if (!ctx) {
    printf("OSMesaCreateContext failed!
");
    return 0;
}

/* Allocate the image buffer */
buffer = (GLfloat *) malloc( WIDTH * HEIGHT * 3 * sizeof(GLfloat));
if (!buffer) {
    printf("Alloc image buffer failed!
");
    return 0;
}

/* Bind the buffer to the context and make it current */
if (!OSMesaMakeCurrent( ctx, buffer, GL_FLOAT, WIDTH, HEIGHT )) {
      printf("OSMesaMakeCurrent failed!
");
      return 0;
}

draw();

printf("RED: %f
", buffer[0]);
printf("GREEN: %f
", buffer[1]);
printf("BLUE: %f
", buffer[2]);

/* free the image buffer */
free( buffer );

/* destroy the context */
OSMesaDestroyContext( ctx );

return 0;
}

在绘画法中,行文如下:

glColor3f(0.5f, 0.56789f, 0.568f);

我应当给我浮动的肤色价值。 我读了彩色,得出以下产出:

channel sizes: 32 32 32 32
RED: 0.501961
GREEN: 0.568627
BLUE: 0.568627

并请注意,0.50 1961=128/255,0.568627=145/255(即固定数目)。

我在我的玉米基础上建造了Mesa:

./configure --with-driver=osmesa --with-osmesa-bits=32 --disable-gallium --disable-egl