Transparent objects casting dark shadows

[LandonRieger]

This has been a great tool, thanks a lot for providing it. I'm having a minor issue with transparent objects casting shadows darker than I would expect. For example, if I set the opacity to zero, I would expect the object to essentially be invisible, but this isn't what I'm seeing. Below is an example of what I mean, adapted from one of the provided examples.

import numpy as np
from plotoptix import NpOptiX
from plotoptix.enums import Geometry
from plotoptix.materials import m_transparent_diffuse
import threading
import copy
from PIL import Image


class params:
    done = threading.Event()


def accum_done(rt: NpOptiX) -> None:
    params.done.set()


def main():

    rt = NpOptiX(on_rt_accum_done=accum_done, width=1000, height=300)
    rt.set_param(min_accumulation_step=500, max_accumulation_frames=500)

    # geometry setup
    box_size = 1.5
    panel_size = 1.0
    z = box_size + 0.1  # offset panels a bit in front of boxes
    spacing = (box_size - panel_size) / 2
    vertices = np.array([[0, 0, z], [0, panel_size, z], [panel_size, panel_size, z], [panel_size, 0, z]], np.float32)
    faces = np.array([[0, 1, 2], [2, 3, 0]])
    uvmap = np.array([[0, 0], [0, 1], [1, 1], [1, 0]], np.float32)
    pos = [[0, 0, 0]]  # add a box at origin with no panel in front

    # blueish panel in front of boxes with increasing opacity
    colors = np.ones((2, 2, 4), dtype=np.float32) * 0.5
    colors[:, :, 0] = 0.0
    alphas = [0.0, 0.02, 0.1, 0.5]

    # add the boxes and panels
    for idx, alpha in enumerate(alphas):

        colors[:, :, 3] = alpha
        rt.set_texture_2d(f"mesh_tex_{idx}", colors)

        mat = copy.deepcopy(m_transparent_diffuse)
        mat["ColorTextures"] = [f"mesh_tex_{idx}"]
        rt.setup_material(f"mesh_mat_{idx}", mat)

        x_pos = (idx + 1) * (box_size + spacing)
        rt.set_mesh(
            f"mesh_{idx}",
            pos=vertices + np.array([x_pos + spacing, spacing, 0.0], dtype=np.float32),
            faces=faces,
            uvmap=uvmap,
            mat=f"mesh_mat_{idx}",
        )
        pos.append([x_pos, 0.0, 0.0])

    rt.set_data(
        "plot", 
        geom=Geometry.ParallelepipedsConstSize, 
        pos=np.array(pos, dtype=np.float32), 
        r=box_size, 
        c=0.75
        )
    rt.set_ambient(0.9)

    x_camera = ((len(alphas) + 1) * (box_size + spacing)) / 2
    rt.setup_camera(
        name="camera1", 
        eye=[x_camera, box_size / 2, 10.0], 
        target=[x_camera, box_size / 2, 0], 
        fov=20
        )

    rt.start()

    if params.done.wait(10):
        print("frame 1 done")
    else:
        print("timeout")

    Image.fromarray(np.array(rt._raw_rgba * 255, dtype=np.uint8), mode="RGBA").save("frame_1.png")
    params.done.clear()
    rt.close()


if __name__ == "__main__":
    main()

[robertsulej]

OK, I see, I'll have a look and let you know.