A buffer offset of 0 is correct since it is relative to VBO's memory which is
bound just above the lines you pasted down below.
________________________________________
Fra: Narayanarao Rao [nar...@gmail.com]
Sendt: 6. november 2013 11:02
To: Sletta Gunnar
Cc: Interest@qt-project.org
Emne: Re: [Interest] Qt 5.2 scenegraph does not draw anything for our MIPS
cpu/VIVANTE GPU platform
Thanks for the reply. I only said they look similar, not the same. Of course, I
do not understand OpenGL very well. I am now trying to read and understand what
each line of the apitrace means and write a standalone opengl c app that only
makes those calls.
I am relatively new to opengl, so bear with me..
One difference I found in the traces is the following sequence of calls:
194 glEnableVertexAttribArray(index = 0)
195 glEnableVertexAttribArray(index = 1)
196 glEnableVertexAttribArray(index = 2)
197 glUseProgram(program = 1)
198 glBindTexture(target = GL_TEXTURE_2D, texture = 1)
199 glUniformMatrix4fv(location = 0, count = 1, transpose = GL_FALSE, value =
{0.0015625, 0, 0, 0, 0, -0.002777778, 0, 0, 0, 0, 1, 0, -1, 1, 0, 1})
200 glVertexAttribPointer(index = 0, size = 2, type = GL_FLOAT, normalized =
GL_FALSE, stride = 16, pointer = NULL)
202 glFlush()
201 glDrawElements(mode = GL_TRIANGLE_STRIP, count = 6, type =
GL_UNSIGNED_SHORT, indices = 0x50)
203 glEnable(cap = GL_BLEND)
204 glDepthMask(flag = GL_FALSE)
205 glBlendFunc(sfactor = GL_ONE, dfactor = GL_ONE_MINUS_SRC_ALPHA)
206 glDisableVertexAttribArray(index = 0)
207 glDisableVertexAttribArray(index = 1)
208 glDisableVertexAttribArray(index = 2)
The above trace is for the non-working case. glVertexAttribPointer is NULL. Is
this expected? I am still trying to workout where in Qt this call is being made
from.
The corresponding trace for the working case (qmlscene without qml)
309 glEnableVertexAttribArray(index = 1)
310 glEnableVertexAttribArray(index = 0)
311 glBindTexture(target = GL_TEXTURE_2D, texture = 1)
312 glUniform1i(location = 1, v0 = 1)
313 glVertexAttribPointer(index = 0, size = 2, type = GL_FLOAT, normalized =
GL_FALSE, stride = 8, pointer = blob(32))
314 glDrawArrays(mode = GL_TRIANGLE_FAN, first = 0, count = 4)
315 glBindTexture(target = GL_TEXTURE_2D, texture = 0)
316 glDisableVertexAttribArray(index = 1)
317 glDisableVertexAttribArray(index = 0)
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