Extra vertex data not properly transfered to vertex shader?

Scripting Issues
1

I discovered a strange behaviour while testing “software” points, if I try to send to the shader extra vertex data, the shader receive a constant random value.

Here is some code, if the point color is from p3d_Color, everything is fine, the points shade from green to red, if I uncomment the line for the extra data, the line is a solid color, red on my computer.

from panda3d.core import *
from math import pi, cos, sin


from direct.directbase import DirectStart

def shader():
    return Shader.make(Shader.SL_GLSL,
                       vertex="""
#version 410

uniform mat4 p3d_ProjectionMatrix;
uniform mat4 p3d_ModelViewMatrix;

in vec4 p3d_Vertex;
in vec4 p3d_Color;
in vec4 extra;
out vec4 color;

void main() {
    gl_Position = p3d_ProjectionMatrix * (p3d_ModelViewMatrix * p3d_Vertex);
    //Uncomment to see the correct colors.
    //color = p3d_Color;
    //Uncomment to see the wrong color
    color = extra;
}
""",
                       fragment="""
#version 410

in vec4 color;
out vec4 frag_color;

void main() {
    frag_color = color;
}
""")

def make_geom(points, colors, size):
    array = GeomVertexArrayFormat()
    array.add_column(InternalName.make('vertex'), 3, Geom.NTFloat32, Geom.CPoint)
    array.add_column(InternalName.make('color'), 4, Geom.NTFloat32, Geom.CColor)
    array.add_column(InternalName.make('size'), 1, Geom.NTFloat32, Geom.COther)
    array.add_column(InternalName.make('extra'), 4, Geom.NTFloat32, Geom.COther)
    format = GeomVertexFormat()
    format.addArray(array)
    format = GeomVertexFormat.registerFormat(format)
    vdata = GeomVertexData('vdata', format, Geom.UH_static)
    vwriter = GeomVertexWriter(vdata, 'vertex')
    colorwriter = GeomVertexWriter(vdata, 'color')
    sizewriter = GeomVertexWriter(vdata, 'size')
    extrawriter = GeomVertexWriter(vdata, 'extra')
    geompoints = GeomPoints(Geom.UH_static)
    for index, (point, color) in enumerate(zip(points, colors)):
        vwriter.add_data3(point)
        colorwriter.add_data4(color)
        sizewriter.add_data1(size)
        extrawriter.add_data4(color)
        geompoints.add_vertex(index)
    geom = Geom(vdata)
    geom.add_primitive(geompoints)
    return geom

size = 1000
points = []
colors = []
for i in range(size):
    theta = pi * i / size
    x = cos(theta)
    y = sin(theta)
    z = 0
    points.append(LPoint3(x, y, z))
    a = i / size
    colors.append(LColor(1 - a, a, 0, 1))

geom = make_geom(points, colors, 4)
gnode = GeomNode('gnode')
gnode.add_geom(geom)
np = NodePath(gnode)
np.set_shader(shader())

np.reparent_to(render)

base.cam.set_pos(0, -1, 0)
base.run()
2

It looks like the munge_points_to_quads code in Panda doesn’t support extra columns.
If I disable the “software” point size stuff, it works:

sattr = ShaderAttrib.make(shader())
sattr = sattr.set_flag(ShaderAttrib.F_shader_point_size, True)
np.set_attrib(sattr)

And indeed, it looks like the code only handles a hardcoded bunch:

Please file a GitHub issue for the munge_points_to_quads bug, thanks!

3

Thanks, I will create the issue. I was afraid that was the problem, and hardware points are not a workaround for me as their size are limited (and the limit depends hardware)

4

Here is the issue on Github : https://github.com/panda3d/panda3d/issues/870