1puts "========" 2puts "Per-pixel lighting using GLSL program (Phong shading), check lighting of back faces" 3puts "========" 4 5pload MODELING VISUALIZATION 6 7# create box 8box b 1 2 3 9explode b F 10 11# draw box 12vclear 13vclose ALL 14vinit View1 15vsetdispmode 1 16vaxo 17vdisplay b_1 b_2 18vfit 19vrotate 0.2 0.0 0.0 20 21# take snapshot with fixed pipeline 22vdump $::imagedir/${::casename}_OFF.png 23set aColorB [vreadpixel 150 150 rgb name] 24set aColorF [vreadpixel 250 250 rgb name] 25if { "$aColorB" != "$aColorF"} { puts "Error: front/back colors are different!" } 26set aColorFixed $aColorF 27 28# activate phong shader 29vshaderprog phong 30set aColorB [vreadpixel 150 150 rgb name] 31set aColorF [vreadpixel 250 250 rgb name] 32if { "$aColorB" != "$aColorF"} { puts "Error: front/back colors are different!" } 33if { "$aColorF" != "$aColorFixed"} { puts "Error: colors are different!" } 34vdump ${imagedir}/${casename}.png 35