Snippet demonstrating vertex pulling in Panda3D

vertex-pulling.py

from panda3d.core import *
#load_prc_file_data("", "gl-version 3 3")

from array import array

# Create two silly triangles.
data = array('f', [
    0, 4, 0,
    1, 4, 1,
    0, 4, 1,

    -2, 4, -1,
    1, 4, 2,
    -2, 4, 1,
])
num_verts = len(data) // 3

# Create a buffer texture and initialize it with the data.
tex = Texture("vertex-data")
tex.setup_buffer_texture(num_verts, Texture.T_float, Texture.F_rgb32, GeomEnums.UH_static)
tex.set_ram_image(data.tobytes())

# Create a dummy vertex data object.
if True:
    format = GeomVertexFormat.get_empty()
    vdata = GeomVertexData('abc', format, GeomEnums.UH_static)
else:
    # Before 1.10, you needed to do this instead:
    aformat = GeomVertexArrayFormat("vertex", 1, GeomEnums.NT_uint8, GeomEnums.C_other)
    format = GeomVertexFormat.register_format(GeomVertexFormat(aformat))
    vdata = GeomVertexData('abc', format, GeomEnums.UH_static)
    vdata.set_num_rows(num_verts)

# This represents a draw call, indicating how many vertices we want to draw.
tris = GeomTriangles(GeomEnums.UH_static)
tris.add_next_vertices(num_verts)

# We need to set a bounding volume so that Panda doesn't try to cull it.
# You could be smarter about this by assigning a bounding volume that encloses
# the vertices.
geom = Geom(vdata)
geom.add_primitive(tris)
geom.set_bounds(OmniBoundingVolume())

node = GeomNode("node")
node.add_geom(geom)

shader = Shader.make(Shader.SL_GLSL, """
#version 140

uniform samplerBuffer vdata;

uniform mat4 p3d_ModelViewProjectionMatrix;

void main() {
  vec4 vertex = texelFetch(vdata, gl_VertexID);

  gl_Position = p3d_ModelViewProjectionMatrix * vertex;
}
""", """
#version 140

void main() {
  // Just paint each triangle with a solid red color.
  gl_FragColor = vec4(1, 0, 0, 1);
}
""")

from direct.showbase.ShowBase import ShowBase

base = ShowBase()

# Put our node in the scene graph and apply the texture containing the data.
path = base.render.attach_new_node(node)
path.set_shader(shader)
path.set_shader_input('vdata', tex)

base.run()