minimum needed to render VertexDomains?

[Josh]

Hi all,

I have what (I thought) is a MWE for drawing primitives with a VertexDomain:

import pyglet
from pyglet.gl import *

if __name__ == '__main__':

    display = pyglet.window.Window(400, 400)


    domain = pyglet.graphics.vertexdomain.create_domain('v2i/stream', 'c4b/stream')
    vertex_list = domain.create(4)
    vertex_list.vertices = [50, 50, 50, 100, 100, 100, 100, 50]
    vertex_list.colors = [
                        255, 255, 255, 255,
                        255, 0, 0, 255,
                        0, 255, 0, 255,
                        0, 0, 255, 255
    ]

    @display.event
    def on_draw():
        display.clear()
        pyglet.graphics.draw(1, GL_POINTS, ('v2i',(10,20)))
        domain.draw(GL_POINTS)
               
    pyglet.app.run()

However, while the single pixel drawn directly by pyglet.graphics.drawshows up, the points from the vertex domain don't. What am I missing?

[Neon22]

I might be reading the opengl docs wrong (and I'm not familiar with vertexdomains) but don't you need normals, or a shader as well/instead ?

[Joshua Dempster]

It's certainly possible, I don't know much about OpenGL. But it doesn't look like much else is happening when, say, a sprite is rendered, except a texture is bound. I don't think it should be necessary to bind textures to draw points? Adding normals doesn't help, neither does enabling blend or disabling lighting.

On Thu, Aug 23, 2018 at 5:50 AM Neon22 <neon...@gmail.com> wrote:

I might be reading the opengl docs wrong (and I'm not familiar with vertexdomains) but don't you need normals, or a shader as well/instead ?

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[Benjamin Moran]

Hi Josh,




There is a typo with the vertex color type. It looks like you want to use 8bit values, so If you change c4b to c4B it should work.




By the way, is there a specific reason you're using Domains directly, instead of just creating a Batch? There is nothing wrong with your approach, but using a Batch might save a bit of boilerplate.

-Ben

[Joshua Dempster]

Thanks Ben! No reason not to use batches, just trying to understand the low-level module.

[Joshua Dempster]

Is there a more efficient way to update large vertex list buffers than vertex_list.attribute = some_iterable? For example, I'm guessing that by default vertex_list.set_attribute is converting the iterable to a ctypes array at some point. If I have the data in a numpy array and access it directly as a ctypes array, could I skip this step?

[Benjamin Moran]

Hi Josh,

If you look at the AbstractAttribute class in pyglet/graphics/vertexattribute.py, it might shed some light on things.

The vertex_list attributes are just ctype arrays, which are part of a large buffer. If you look at `domain.attributes`, you can find the buffers there. 

You should be able to move the data directly into those buffers.