Below a simple example to trigger this problem (in Python/PyQT/PyOpenGL for simplicity)
#! /usr/bin/env python
import numpy as np
from numpy.linalg import norm
import OpenGL
import OpenGL.GL as gl
import OpenGL.GLU as glu
import OpenGL.GLUT as glut
from PyQt4 import QtGui, QtCore
from PyQt4.QtOpenGL import *
from math import *
import sys
_vsSphere = """#version 440 compatibility
#extension GL_ARB_shader_storage_buffer_object : require
smooth out vec4 vecColor;
void main()
{
vec3 vecVertex = gl_Vertex.xyz + vec3(0,0,-1);
gl_Position = gl_ProjectionMatrix * gl_ModelViewMatrix * vec4(vecVertex,1.0);
vecColor.rgb = vecVertex.xyz * 0.5 + 0.5;
vecColor.a = 1.0;
}
"""
_fsSphere = """#version 440 compatibility
smooth in vec4 vecColor;
void main()
{
gl_FragColor = vecColor;
}
"""
_vsSphereSSBO3 = """#version 440 compatibility
#extension GL_ARB_shader_storage_buffer_object : require
layout (std430, binding = 0) buffer VertexPositionBufferIn
{
vec3 pos[];
} ;
smooth out vec4 vecColor;
void main()
{
int iIdx = gl_VertexID;
vec3 vecVertex = pos[iIdx].xyz; + vec3(0,0,-1);
gl_Position = gl_ProjectionMatrix * gl_ModelViewMatrix * vec4(vecVertex,1.0);
vecColor.rgb = vecVertex.xyz * 0.5 + 0.5;
vecColor.a = 1.0;
}
"""
_vsSphereSSBO4 = """#version 440 compatibility
#extension GL_ARB_shader_storage_buffer_object : require
layout (std430, binding = 0) buffer VertexPositionBufferIn
{
vec4 pos[];
} ;
smooth out vec4 vecColor;
void main()
{
int iIdx = gl_VertexID;
vec3 vecVertex = pos[iIdx].xyz; + vec3(0,0,-1);
gl_Position = gl_ProjectionMatrix * gl_ModelViewMatrix * vec4(vecVertex,1.0);
vecColor.rgb = vecVertex.xyz * 0.5 + 0.5;
vecColor.a = 1.0;
}
"""
fEpsilon = 0.0000001
mode="va"
mode="vbo"
mode="ssbo4"
#mode="ssbo3"
sphereGeometry = True
def onSphere(az,el):
fProjectionLength = abs(cos(el))
fProjectionX = cos(az) * fProjectionLength
if abs(fProjectionX) < fEpsilon:
fProjectionX = 0.0
fProjectionZ = -sin(az) * fProjectionLength
if abs(fProjectionZ) < fEpsilon:
fProjectionZ = 0.0
fProjectionX2 = (fProjectionX*fProjectionX)
fProjectionZ2 = (fProjectionZ*fProjectionZ)
fProjectionXZ2 = fProjectionX2 + fProjectionZ2
fProjectionY = sqrt(1.0 - fProjectionXZ2 )
if (el < 0.0):
fProjectionY = -fProjectionY
if abs(fProjectionY) < fEpsilon:
fProjectionY = 0.0
point = (fProjectionX,fProjectionY,fProjectionZ)
return point
class Viewer3DWidget(QGLWidget):
def __init__(self, parent):
QGLWidget.__init__(self, parent)
self.uWidth = 0
self.uHeight = 0
self.iVertexSize = 3
if (mode is "ssbo4"):
self.iVertexSize = 4
self.vbo = None
self.vecBackgroundColor = (1.,1.,1.)
self.iSubdivision = 3
self.data = np.zeros((1,self.iVertexSize),dtype=np.float32)
self.dataLinear = self.data.reshape(self.data.size)
self.bRegenerate = True
self.iCnt = 0
def setSubdivision(self, iVal):
self.iSubdivision = iVal
self.bRegenerate = True
self.update()
def regenerateGeometry(self):
if (not self.bRegenerate):
return
else:
self.bRegenerate = False
if sphereGeometry:
iTotalTriangles = (self.iSubdivision - 2)*(self.iSubdivision *2) #+ (self.iSubdivision * 2) # skipping the top and the bottom
self.data = np.ones((iTotalTriangles * 3,self.iVertexSize),dtype=np.float32) #ones to get the last component of vec4 to 1
fAzSlab = 2.0 * pi / float(self.iSubdivision)
fElSlab = pi / float(self.iSubdivision)
self.iCnt = 0
for i in range(1,self.iSubdivision-1):
for j in range(self.iSubdivision):
fAz0 = fAzSlab * j
fAz1 = fAzSlab * (j + 1)
fEl0 = -(fElSlab * i) + pi * 0.5
fEl1 = -(fElSlab * (i + 1)) + pi * 0.5
point = onSphere(fAz0,fEl1)
self.data[self.iCnt,0] = float(point[0])
self.data[self.iCnt,1] = float(point[1])
self.data[self.iCnt,2] = float(point[2])
self.iCnt += 1
point = onSphere(fAz1,fEl1)
self.data[self.iCnt,0] = float(point[0])
self.data[self.iCnt,1] = float(point[1])
self.data[self.iCnt,2] = float(point[2])
self.iCnt += 1
point = onSphere(fAz1,fEl0)
self.data[self.iCnt,0] = float(point[0])
self.data[self.iCnt,1] = float(point[1])
self.data[self.iCnt,2] = float(point[2])
self.iCnt += 1
point = onSphere(fAz1,fEl0)
self.data[self.iCnt,0] = float(point[0])
self.data[self.iCnt,1] = float(point[1])
self.data[self.iCnt,2] = float(point[2])
self.iCnt += 1
point = onSphere(fAz0,fEl0)
self.data[self.iCnt,0] = float(point[0])
self.data[self.iCnt,1] = float(point[1])
self.data[self.iCnt,2] = float(point[2])
self.iCnt += 1
point = onSphere(fAz0,fEl1)
self.data[self.iCnt,0] = float(point[0])
self.data[self.iCnt,1] = float(point[1])
self.data[self.iCnt,2] = float(point[2])
self.iCnt += 1
self.dataLinear = self.data.reshape(self.data.size)
print self.iCnt, self.dataLinear.size, self.dataLinear.shape
else:
self.data = np.ones((3,self.iVertexSize),dtype=np.float32)
self.data[0,0] = -0.5
self.data[0,1] = -0.5
self.data[0,2] = 0.0
self.data[1,0] = 0.5
self.data[1,1] = -0.5
self.data[1,2] = 0.0
self.data[2,0] = 0.0
self.data[2,1] = 0.5
self.data[2,2] = 0.0
self.dataLinear = self.data.reshape(self.data.size)
if (self.vbo is None):
self.vbo = gl.glGenBuffers(1)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, self.vbo)
gl.glBufferData(gl.GL_ARRAY_BUFFER, self.dataLinear, gl.GL_DYNAMIC_DRAW)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, gl.GLuint(0))
#
def initializeGL(self):
self.shaShaderSphere = QGLShaderProgram(self.context())
self.shaShaderSphere.addShaderFromSourceCode(QGLShader.Vertex, _vsSphere)
self.shaShaderSphere.addShaderFromSourceCode(QGLShader.Fragment, _fsSphere)
self.shaShaderSphere.link()
self.shaShaderSphereSSBO3 = QGLShaderProgram(self.context())
self.shaShaderSphereSSBO3.addShaderFromSourceCode(QGLShader.Vertex, _vsSphereSSBO3)
self.shaShaderSphereSSBO3.addShaderFromSourceCode(QGLShader.Fragment, _fsSphere)
self.shaShaderSphereSSBO3.link()
self.shaShaderSphereSSBO4 = QGLShaderProgram(self.context())
self.shaShaderSphereSSBO4.addShaderFromSourceCode(QGLShader.Vertex, _vsSphereSSBO4)
self.shaShaderSphereSSBO4.addShaderFromSourceCode(QGLShader.Fragment, _fsSphere)
self.shaShaderSphereSSBO4.link()
gl.glClearColor(0, 0, 0, 1.0)
gl.glClearDepth(1.0)
def paintGL(self):
if (self.uWidth is 0):
return
self.regenerateGeometry()
gl.glMatrixMode( gl.GL_PROJECTION )
gl.glLoadIdentity()
gl.glOrtho(-2,2,-2,2,0,3)
gl.glMatrixMode( gl.GL_MODELVIEW );
gl.glLoadIdentity();
# glDisable(GL_BLEND)
# glDisable(GL_DEPTH_TEST);
# glDisable(GL_LIGHTING)
gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)
gl.glColor(1.0, 1.0,1.0)
gl.glEnable(gl.GL_DEPTH_TEST)
gl.glDepthFunc(gl.GL_LESS);
if (mode == "vbo"):
self.drawSphereVBO()
elif(mode == "va"):
self.drawSphereArray()
elif(mode == "ssbo3"):
self.drawSphereSSBO3()
elif(mode == "ssbo4"):
self.drawSphereSSBO4()
def drawSphereArray(self):
shaShader = self.shaShaderSphere
shaShader.bind()
gl.glEnableClientState(gl.GL_VERTEX_ARRAY);
gl.glVertexPointer(3, gl.GL_FLOAT, 0, self.dataLinear);
#gl.glDrawArrays(gl.GL_TRIANGLES,0,self.iCnt);
gl.glDrawArrays(gl.GL_TRIANGLES,0,self.dataLinear.size / 3);
gl.glDisableClientState(gl.GL_VERTEX_ARRAY);
shaShader.release()
def drawSphereVBO(self):
shaShader = self.shaShaderSphere
shaShader.bind()
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, self.vbo)
gl.glEnableClientState(gl.GL_VERTEX_ARRAY);
gl.glVertexPointer(3, gl.GL_FLOAT, 0, None);
gl.glDrawArrays(gl.GL_TRIANGLES,0,self.dataLinear.size / 3);
gl.glDisableClientState(gl.GL_VERTEX_ARRAY);
gl.glBindBuffer(gl.GL_ARRAY_BUFFER,gl.GLuint(0))
shaShader.release()
def drawSphereSSBO3(self):
shaShader = self.shaShaderSphereSSBO3
shaShader.bind()
gl.glBindBufferBase(gl.GL_SHADER_STORAGE_BUFFER, 0, self.vbo);
gl.glDrawArrays(gl.GL_TRIANGLES,0,self.dataLinear.size / 3);
gl.glBindBufferBase(gl.GL_SHADER_STORAGE_BUFFER, 0, 0);
shaShader.release()
def drawSphereSSBO4(self):
shaShader = self.shaShaderSphereSSBO4
shaShader.bind()
gl.glBindBufferBase(gl.GL_SHADER_STORAGE_BUFFER, 0, self.vbo);
gl.glDrawArrays(gl.GL_TRIANGLES,0,self.dataLinear.size / 4);
gl.glBindBufferBase(gl.GL_SHADER_STORAGE_BUFFER, 0, 0);
shaShader.release()
def resizeGL(self, widthInPixels, heightInPixels):
if ((widthInPixels is not self.uWidth) or (heightInPixels is not self.uHeight)):
self.uWidth = widthInPixels
self.uHeight = heightInPixels
gl.glViewport(0, 0, widthInPixels, heightInPixels)
self.update()
class TestSSBOs(QtGui.QMainWindow):
def __init__(self):
QtGui.QMainWindow.__init__(self)
self.setWindowTitle('TestSSBOs')
self.statusBar().showMessage("Hello there")
exit = QtGui.QAction("Exit", self)
exit.setShortcut("Ctrl+Q")
exit.setStatusTip('Exit application')
self.connect(exit, QtCore.SIGNAL('triggered()'), QtCore.SLOT('close()'))
self.setToolTip('This is a window, or <b>something</b>')
self.viewer3D = Viewer3DWidget(self)
parentWidget = QtGui.QWidget()
slider1 = QtGui.QSlider(QtCore.Qt.Horizontal, None)
slider1.setRange(3,50)
slider1.setValue(0)
slider1.setMaximumWidth(120)
slider1.valueChanged.connect(self.slider1Handler)
vbox = QtGui.QVBoxLayout()
vbox.addWidget(slider1)
vbox.addStretch(1)
self.viewer3D.setSizePolicy( QtGui.QSizePolicy.Expanding, QtGui.QSizePolicy.Expanding )
hbox = QtGui.QHBoxLayout()
hbox.addLayout(vbox)
hbox.addWidget(self.viewer3D)
parentWidget.setLayout(hbox)
self.setCentralWidget(parentWidget)
self.resize(500,500)
def closeEvent(self, event):
event.accept()
def slider1Handler(self, iVal):
self.viewer3D.setSubdivision(iVal)
if __name__ == '__main__':
# app = QtGui.QApplication(['Python Qt OpenGL Demo'])
app = QtGui.QApplication(sys.argv)
window = TestSSBOs()
window.show()
sys.exit(app.exec_())
