[Mesa3d-dev] [ mesa3d-Bugs-437376 ] Incorrect lighting for NURBS surface

[<no...@so...>]

Bugs item #437376, was opened at 2001-06-29 07:46
You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=100003&aid=437376&group_id=3

Category: GLU
Group: Rendering Error
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: Incorrect lighting for NURBS surface

Initial Comment:
Mesa version: 3.5 (using SI-GLU)

Nurbs surfaces are incorrectly lighted. A few
rectangles of the mesh are wrongly shaded. The number
and position of the stains depends on the size and
orientation of the surface. This didn't happen with
Mesa 3.4.x.

[This bug is different from #212069.]

MESA_INFO gives:

X/Mesa visual = 0x8050c88
X/Mesa dithered pf = 13
X/Mesa undithered pf = 6
X/Mesa level = 0
X/Mesa depth = 16
X/Mesa bits per pixel = 16
X/Mesa visual = 0x8050c88
X/Mesa dithered pf = 13
X/Mesa undithered pf = 6
X/Mesa level = 0
X/Mesa depth = 16
X/Mesa bits per pixel = 16
Mesa GL_VERSION = 1.2 Mesa 3.5
Mesa GL_RENDERER = Mesa X11
Mesa GL_VENDOR = Brian Paul
Mesa GL_EXTENSIONS = GL_ARB_imaging GL_ARB_multitexture
GL_ARB_texture_border_clamp GL_ARB_texture_compression
GL_ARB_texture_cube_map GL_ARB_texture_env_add
GL_ARB_texture_env_combine GL_ARB_texture_env_dot3
GL_ARB_transpose_matrix GL_EXT_abgr GL_EXT_bgra
GL_EXT_blend_color GL_EXT_blend_func_separate
GL_EXT_blend_logic_op GL_EXT_blend_minmax
GL_EXT_blend_subtract GL_EXT_clip_volume_hint
GL_EXT_convolution GL_EXT_compiled_vertex_array
GL_EXT_fog_coord GL_EXT_histogram GL_EXT_packed_pixels
GL_EXT_paletted_texture GL_EXT_point_parameters
GL_EXT_polygon_offset GL_EXT_rescale_normal
GL_EXT_secondary_color GL_EXT_shared_texture_palette
GL_EXT_stencil_wrap GL_EXT_texture3D
GL_EXT_texture_env_add GL_EXT_texture_env_combine
GL_EXT_texture_env_dot3 GL_EXT_texture_object
GL_EXT_texture_lod_bias GL_EXT_vertex_array
GL_HP_occlusion_test GL_INGR_blend_func_separate
GL_MESA_resize_buffers GL_MESA_window_pos
GL_NV_blend_square GL_NV_texgen_reflection
GL_SGI_color_matrix GL_SGI_color_table
GL_SGIS_generate_mipmap GL_SGIS_pixel_texture
GL_SGIS_texture_border_clamp GL_SGIS_texture_edge_clamp
GL_SGIX_depth_texture GL_SGIX_pixel_texture
GL_SGIX_shadow GL_SGIX_shadow_ambient
Mesa thread-safe: YES
Mesa x86-optimized: YES
Mesa sparc-optimized: NO

There is also some output:

arc_ccw_turn, p = 0
case b
arc_ccw_turn, p = 0
case d
arc_ccw_turn, p = 0
case a
arc_ccw_turn, p = 0
case c
[...]

Example:

#include <cmath>
#include <cstdlib>
#include <GL/glut.h>

double wx = 0; // rotation along x-axis
double wy = 0; // rotation along y-axis
double s  = 1; // scaling factor

GLUnurbsObj* nobj;

void init()
{
  GLfloat light0[4] = { 0.0, 0.0, 10.0, 1.0 };
  glLightfv (GL_LIGHT0, GL_POSITION, light0);
  glEnable (GL_LIGHT0);

  glEnable(GL_DEPTH_TEST);
  glEnable(GL_AUTO_NORMAL);
  glEnable(GL_NORMALIZE);
  glEnable(GL_LIGHTING);

  nobj = gluNewNurbsRenderer();
}

void draw()
{
  /* knot vectors */
  GLfloat U[12] = { 0, 0, 0, 0.25, 0.25, 0.5, 0.5,
0.75, 0.75, 1, 1, 1 };
  GLfloat V[8]  = { 0, 0, 0, 0.5,  0.5, 1, 1, 1 };

  /* control points */
  GLfloat a = 0.5*sqrt(2);
  GLfloat b = 0.5;
  GLfloat P[45][4] = { {1, 0, 0, 1 }, {a,  a,  0, a},
{0,  1,  0, 1}, {-a,  a,  0, a}, {-1, 0, 0, 1},
                       {a, 0, 0, a }, {b,  b,  b, b},
{0,  a,  a, a}, {-b,  b,  b, b}, {-a, 0, 0, a},
                       {1, 0, 0, 1 }, {a,  0,  a, a},
{0,  0,  1, 1}, {-a,  0,  a, a}, {-1, 0, 0, 1},
                       {a, 0, 0, a }, {b, -b,  b, b},
{0, -a,  a, a}, {-b, -b,  b, b}, {-a, 0, 0, a},
                       {1, 0, 0, 1 }, {a, -a,  0, a},
{0, -1,  0, 1}, {-a, -a,  0, a}, {-1, 0, 0, 1},
                       {a, 0, 0, a }, {b, -b, -b, b},
{0, -a, -a, a}, {-b, -b, -b, b}, {-a, 0, 0, a},
                       {1, 0, 0, 1 }, {a,  0, -a, a},
{0,  0, -1, 1}, {-a,  0, -a, a}, {-1, 0, 0, 1},
                       {a, 0, 0, a }, {b,  b, -b, b},
{0,  a, -a, a}, {-b,  b, -b, b}, {-a, 0, 0, a},
                       {1, 0, 0, 1 }, {a,  a,  0, a},
{0,  1,  0, 1}, {-a,  a,  0, a}, {-1, 0, 0, 1} };

  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  glPushMatrix();

  glRotated(wy,0,1,0);
  glRotated(wx,1,0,0);
  glScaled(s,s,s);

  gluBeginSurface(nobj);
  gluNurbsSurface(nobj, 12, U, 8, V, 5*4, 4, &P[0][0],
3, 3, GL_MAP2_NORMAL);
  gluNurbsSurface(nobj, 12, U, 8, V, 5*4, 4, &P[0][0],
3, 3, GL_MAP2_VERTEX_4);
  gluEndSurface(nobj);

  glPopMatrix();
  glutSwapBuffers();
}

int main(int argc, char **argv)
{
  if (argc>=4)
    {
      s  = atof(argv[1]);
      wx = atof(argv[2]);
      wy = atof(argv[3]);
    }

  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE |
GLUT_DEPTH);
  glutInitWindowSize(600,600);
  glutInitWindowPosition(0,0);
  glutCreateWindow(argv[0]);
  glutDisplayFunc(draw);

  init();

  glutMainLoop();
  return 0;
}




----------------------------------------------------------------------

Comment By: Joachim Reichel (reichel)
Date: 2001-06-29 07:54

Message:
Logged In: YES 
user_id=28760

Oops, wasn't logged in.
Submitted by: Joachim Reichel (reichel)
Email: joa...@gm...

----------------------------------------------------------------------

You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=100003&aid=437376&group_id=3