>> even for simple convex polygons. Correction, I am talking rubbish. For a convex polygon it is easily broken down to a single strip or fan. I intended to say something like 'for simple (ie. planar) non-convex polygons'
:-) On Nov 15, 3:43 pm, Jonathan Hartley <[EMAIL PROTECTED]> wrote: > Hey. > > Don't discount using simple GL_TRIANGLES. On first glance they seem > inefficient, because you have to send n*3 vertices as opposed to (2 + > n) for GL_TRIANGLE_STRIPs or FANs. However: > > 1) If you used *indexed* vertex lists, then my small scale personal > experiments seem to show that they are not slower, despite you having > to send more vertices to render the same thing. Graphics cards > apparently notice when you use the same indexed vertex again, and re- > use the old cached vertex calculation results, so sending the same > vertex for several adjacent triangles doesn't actually seem to slow > things down. In fact, on two of the five computers I have tried it on, > it actually speeds things up. I am guessing those particular graphics > cards are optimised for the case of GL_TRIANGLES because it is common. > > 2) You can easily draw several discontinuous shapes in a single > GL_TRIANGLES primitive. This is not possible using GL_TRIANGLE_STRIPs > or FANs. So you send fewer primitives. > > 3) GL_TRIANGLES require much less messing around preparing your data. > You don't need to try and decompose all your polygons into an optimal > number of STRIP or FAN primitives, which is a non-trivial exercise, > even for simple convex polygons. No doubt there are tools out there > that could do this sort of thing for you, but I prefer to KISS, and > see no reason to add this extra wrinkle of complexity unless there was > a compelling benefit, which I don't believe there is. > > I have no experience with trying to use GL_POLYGONS. That might be > really viable and I'm sure other people can comment on their strengths > and weaknesses. > > Also: I have seen very lacklustre performance using pyglet's > vertex_list.draw() (identical to explicit glVertex() calls). I would > highly recommend using batches instead, which are much faster, for > reasons unknown to me. Maybe batches use VBOs under the covers, and > vertex lists do not. I speculate. > > This whole topic has perplexed me, trying to figure out the optimal > intended usage patterns for pyglet, and I'd love to hear other > people's contributions and corrections to my opinions. > > Best, > > Jonathan > > On Nov 15, 10:32 am, vaibhav <[EMAIL PROTECTED]> wrote: > > > I am trying to draw two consecutive primitives (circles) in the same > > batch and it says in the drawing modes section (below) that > > gl_polygon, gl_line_loop or gl_triangle_fan cannot be used. so i was > > wondering what winding could i use to draw a circle using one of these > > - GL_LINE_STRIP, GL_TRIANGLE_STRIP or GL_QUAD_STRIP > > >http://pyglet.org/doc/api/pyglet.graphics-module.html > > -------- > > Drawing modes > > > Methods in this module that accept a mode parameter will accept any > > value in the OpenGL drawing mode enumeration; for example, GL_POINTS, > > GL_LINES, GL_TRIANGLES, etc. > > > Because of the way the graphics API renders multiple primitives with > > shared state, GL_POLYGON, GL_LINE_LOOP and GL_TRIANGLE_FAN cannot be > > used --- the results are undefined. > > > When using GL_LINE_STRIP, GL_TRIANGLE_STRIP or GL_QUAD_STRIP care must > > be taken to insert degenrate vertices at the beginning and end of each > > vertex list. For example, given the vertex list: > > > A, B, C, D > > > the correct vertex list to provide the vertex list is: > > > A, A, B, C, D, D > > > Alternatively, the NV_primitive_restart extension can be used if it is > > present. This also permits use of GL_POLYGON, GL_LINE_LOOP and > > GL_TRIANGLE_FAN. Unfortunatley the extension is not provided by older > > video drivers, and requires indexed vertex lists. > > > On Nov 14, 4:26 pm, "Colin Bean" <[EMAIL PROTECTED]> wrote: > > > > On Fri, Nov 14, 2008 at 3:59 PM, Vaibhav. bhawsar > > > > <[EMAIL PROTECTED]> wrote: > > > > > Hi, > > > > Since i cannot use GL_TRIANGLE_FAN or GL_POLYGON in > > > > pyglet.graphics.vertex_list, what would be a good mode to use to draw > > > > a circle? I am not sure what the winding might be to draw a circle if > > > > i used a GL_TRIANGLE_STRIP > > > > > thanks! > > > > > -- > > > > Vaibhav Bhawsar > > > > You can pass any openGL mode you want to vertex_list.draw (or > > > batch.add), so I don't understand why you can't use GL_POLYGON... > > > >http://pyglet.org/doc/api/pyglet.graphics.vertexdomain.VertexList-cla... > > > > Colin --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "pyglet-users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/pyglet-users?hl=en -~----------~----~----~----~------~----~------~--~---
