weird render behavior

[weberhen]

Hi!

I'm puzzled by a simple render script of mine. I have a sphere and an envmap with two source lights symmetrically placed. For some reason, depending on the values of the lights, the final render is not symmetrical, even though the sphere is placed exactly in the middle of the lights. The code bellow reproduces the problem:

import torch
import pyredner
import numpy as np
import cv2

vertices, indices, uvs, normals = pyredner.generate_sphere(theta_steps = 64, phi_steps = 128)
m = pyredner.Material(diffuse_reflectance = torch.tensor((0.5, 0.5, 0.5), device = pyredner.get_device()))
obj = pyredner.Object(vertices = vertices, indices = indices, uvs = uvs, normals = normals, material = m)
cam = pyredner.automatic_camera_placement([obj], resolution = (480, 640))

envmap_img = np.zeros((16, 32, 3)).astype(np.float32)
envmap_img[2:3, 4:5, :] = 1000
envmap_img = envmap_img + np.flip(envmap_img, axis=1)
envmap_img = cv2.resize(envmap_img, (2048, 1024))
envmap_img[envmap_img > 0] = 1000
envmap_img = torch.tensor(envmap_img).to(pyredner.get_device())

pyredner.imwrite(envmap_img.cpu(), '_envmap.png', normalize=True)

envmap = pyredner.EnvironmentMap(envmap_img, directly_visible=False) # *10 to make the image brighter
scene = pyredner.Scene(objects = [obj], camera = cam, envmap=envmap)
img = pyredner.render_pathtracing(scene, num_samples=1024, use_primary_edge_sampling=True, use_secondary_edge_sampling=True)

pyredner.imwrite(img.cpu(), '_render.png', normalize=True)

The above code produce expected result bellow:

But once I comment line envmap_img[envmap_img > 0] = 1000 the result becomes:

Thanks for the help!