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# Mario Rosasco, 2016
# adapted from framework.cpp, Copyright (C) 2010-2012 by Jason L. McKesson
# This file is licensed under the MIT License.
#
# NB: Unlike in the framework.cpp organization, the main loop is contained
# in the tutorial files, not in this framework file. Additionally, a copy of
# this module file must exist in the same directory as the tutorial files
# to be imported properly.
import os
from OpenGL.GL import *
# Function that creates and compiles shaders according to the given type (a GL enum value) and
# shader program (a file containing a GLSL program).
def loadShader(shaderType, shaderFile):
# check if file exists, get full path name
strFilename = findFileOrThrow(shaderFile)
shaderData = None
with open(strFilename, 'r') as f:
shaderData = f.read()
shader = glCreateShader(shaderType)
glShaderSource(shader, shaderData) # note that this is a simpler function call than in C
# This shader compilation is more explicit than the one used in
# framework.cpp, which relies on a glutil wrapper function.
# This is made explicit here mainly to decrease dependence on pyOpenGL
# utilities and wrappers, which docs caution may change in future versions.
glCompileShader(shader)
status = glGetShaderiv(shader, GL_COMPILE_STATUS)
if status == GL_FALSE:
# Note that getting the error log is much simpler in Python than in C/C++
# and does not require explicit handling of the string buffer
strInfoLog = glGetShaderInfoLog(shader)
strShaderType = ""
if shaderType is GL_VERTEX_SHADER:
strShaderType = "vertex"
elif shaderType is GL_GEOMETRY_SHADER:
strShaderType = "geometry"
elif shaderType is GL_FRAGMENT_SHADER:
strShaderType = "fragment"
print("Compilation failure for " + strShaderType + " shader:\n" + str(strInfoLog))
return shader
# Function that accepts a list of shaders, compiles them, and returns a handle to the compiled program
def createProgram(shaderList):
program = glCreateProgram()
for shader in shaderList:
glAttachShader(program, shader)
glLinkProgram(program)
status = glGetProgramiv(program, GL_LINK_STATUS)
if status == GL_FALSE:
# Note that getting the error log is much simpler in Python than in C/C++
# and does not require explicit handling of the string buffer
strInfoLog = glGetProgramInfoLog(program)
print("Linker failure: \n" + str(strInfoLog))
for shader in shaderList:
glDetachShader(program, shader)
return program
# Helper function to locate and open the target file (passed in as a string).
# Returns the full path to the file as a string.
def findFileOrThrow(strBasename):
# Keep constant names in C-style convention, for readability
# when comparing to C(/C++) code.
if os.path.isfile(strBasename):
return strBasename
LOCAL_FILE_DIR = "data" + os.sep
GLOBAL_FILE_DIR = os.path.dirname(os.path.abspath(__file__)) + os.sep + "data" + os.sep
strFilename = LOCAL_FILE_DIR + strBasename
if os.path.isfile(strFilename):
return strFilename
strFilename = GLOBAL_FILE_DIR + strBasename
if os.path.isfile(strFilename):
return strFilename
raise IOError('Could not find target file ' + strBasename)
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