void FindBestDepthBias()
{
#ifdef ANDROID_EDITION
int hardwareType = Android_JNI_GetHardwareType();
Android_JNI_GetPolygonOffset(hardwareType, 1, &polygonOffsetFactor, &polygonOffsetUnits);
#else
float f, bestz = 0.25f;
int x;
if (biasFactor) return;
biasFactor = 64.0f; // default value
glPushAttrib(GL_ALL_ATTRIB_BITS);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_ALWAYS);
glEnable(GL_POLYGON_OFFSET_FILL);
glDrawBuffer(GL_BACK);
glReadBuffer(GL_BACK);
glDisable(GL_BLEND);
glDisable(GL_ALPHA_TEST);
glColor4ub(255,255,255,255);
glDepthMask(GL_TRUE);
for (x=0, f=1.0f; f<=65536.0f; x+=4, f*=2.0f) {
float z;
glPolygonOffset(0, f);
glBegin(GL_TRIANGLE_STRIP);
glVertex3f(float(x+4 - widtho)/(width/2), float(0 - heighto)/(height/2), 0.5);
glVertex3f(float(x - widtho)/(width/2), float(0 - heighto)/(height/2), 0.5);
glVertex3f(float(x+4 - widtho)/(width/2), float(4 - heighto)/(height/2), 0.5);
glVertex3f(float(x - widtho)/(width/2), float(4 - heighto)/(height/2), 0.5);
glEnd();
glReadPixels(x+2, 2+viewport_offset, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &z);
z -= 0.75f + 8e-6f;
if (z<0.0f) z = -z;
if (z > 0.01f) continue;
if (z < bestz) {
bestz = z;
biasFactor = f;
}
//printf("f %g z %g\n", f, z);
}
//printf(" --> bias factor %g\n", biasFactor);
glPopAttrib();
#endif
}
void OGLRender::ApplyZBias(int bias)
{
float f1 = bias > 0 ? -3.0f : 0.0f; // z offset = -3.0 * max(abs(dz/dx),abs(dz/dy)) per pixel delta z slope
float f2 = bias > 0 ? -3.0f : 0.0f; // z offset += -3.0 * 1 bit
#ifdef PAULSCODE
Android_JNI_GetPolygonOffset(hardwareType, bias, &f1, &f2);
#endif
if (bias > 0)
{
glEnable(GL_POLYGON_OFFSET_FILL); // enable z offsets
OPENGL_CHECK_ERRORS;
}
else
{
glDisable(GL_POLYGON_OFFSET_FILL); // disable z offsets
OPENGL_CHECK_ERRORS;
}
glPolygonOffset(f1, f2); // set bias functions
OPENGL_CHECK_ERRORS;
}
