Talk:OpenGL Programming/Scientific OpenGL Tutorial 03


 * The problem now is that we lose the automatic coordinate transformation of before, so we can no longer draw a box with corners (-1, -1) and (1, 1). Unfortunately, there is no easy function (TODO: or is there?) to get the same transformation as glViewport applies,

=> would glm::ortho do the trick? It should be equivalent to http://www.opengl.org/sdk/docs/man/xhtml/gluOrtho2D.xml
 * Well, you could use an orthographic projection to simulate a viewport transformation, but it works the wrong way around, so it would still require you to do most of the maths manually.


 * The box-drawing code need to be updated in the tutorial (you switched to vbo in the code repository graph03/graph.cpp)
 * Ok.


 * The section about drawing the graph and the box could be reordered, to group all graph-related actions (namely: the scissors), then all box related actions.
 * Ok.


 * Not sure I got the exercise about big points - when you say "right outside", for a 100x100 window, do you mean 101x101 or rather 200x200?
 * 101x101 and -1x-1, yes. The idea is that according to the standard, after the vertex processing stage, primitives get clipped to the viewport range, and if you draw GL_POINTS each vertex is its own primitive, so any point outside the viewport is completely culled, even though you would be able to see part of it if you have a pointsize > 1.


 * Drawing major ticks every 2.54 units means that the first major unit is out of the (2.0x2.0) screen.
 * That's correct :)