How to adjust the lighting problem in 3D

Lighting: You must use photometric lights and ensure that the brightness of these lights is within the correct range.

Natural light: To simulate natural light, make sure to use IES Sun and IES Sky. They can give the correct lighting information according to the specific location, date and time.

Material reflectivity: You must ensure that the reflectivity value of the secondary material in the scene is consistent with the reality. For example, the reflectivity of a wall with white paint is about 80%; However, the reflectivity of pure white material (RGB: 255,255,255) is 100%. In this case, you must manually adjust the reflectivity.

Exposure control: exposure control is equivalent to the aperture of the camera. You can use it to control the final rendering result and optimize the rendered image.

Physics-based radiosity workflow using photo photometric lighting;

Check and adjust the size of objects in the scene to match their physical size, and adjust the reflectivity of materials to match their physical properties.

Put photometric lights into the scene. You can place virtual lights just like the real world places lights. For relevant information, please refer to the light brightness table attached to the help.

Select the Render Menu Environment dialog box. Select the exposure type you want to use.

Render the scene to preview the lighting effect. In this step, the light energy transfer is not handled, but you can quickly determine the position and intensity of the direct light and adjust the position and intensity of the direct light.

Choose Rendering menu Advanced Lighting dialog. Select radiosity in the advanced lighting options. (Make sure that the small box in front of Active is checked)

In the Radiometric Parameters rollout, click Start to calculate radiosity. After calculation, you can see the effect in the view. The lighting effect is displayed directly on the geometry, so the adjustment can be easily observed in the view without recalculation.

Click Render Scene again. The renderer calculates direct light and shadows to complete the rendering work. Based on physical properties, you can create a scene without using lights, but you must pay attention to the following points:

Natural lighting: If you don't want to use physics-based lighting types to simulate natural light, you can use direct light to simulate sunlight and skylight to simulate skylight.

Exposure control: Because standard lighting is not based on precise physics, you only need to adjust the result of light energy transfer without affecting direct lighting. Using logarithmic exposure control, only turning on the indirect lighting function can control the result of light transmission by using the brightness contrast function of exposure control.

Radiometric workflow of standard lighting:

Ensure that the size of the geometry in the scene matches the actual size.

Place standard lights in your scene.

Render the scene preview light. In this step, the light energy transfer is not handled, but you can quickly determine the position and intensity of the direct light and adjust the position and intensity of the direct light.

Choose Rendering menu Advanced Lighting dialog. Select radiosity in the advanced lighting options. (Make sure that the small box in front of Active is checked)

In the Radiometric Parameters rollout, click Start to calculate radiosity. After calculation, you can see the effect in the view. The lighting effect is displayed directly on the geometry, so the adjustment can be easily observed in the view without recalculation.

Select the Render Menu Environment dialog box. Select the exposure type you want to use.

When using standard light in radiosity, make sure to use logarithmic exposure control and select "Only Correct and Direct", which will make exposure control only affect radiosity effect. In this way, you can use brightness and contrast control to adjust the indirect light effect without affecting the direct light, so that the light energy transfer effect can be controlled in the correct range.

Click Render Scene again. The renderer calculates direct light and shadows to complete the rendering work.

By default, radiosity calculates the current frame. If there are animated objects in the scene, or you need to transmit light to calculate each frame of the animation, please select the option of Calculate Radioactivity in the Render Scene dialog box.

In the process of animation calculation, when the object moves or the light changes, it is necessary to recalculate the ray tracing calculation in each frame. If there is no change between two frames, the rendering engine will not perform radiosity calculation.

Keep in mind that flicker may occur between animation frames because the rendering engine uses random statistical sampling.

Tip: Before radiosity calculates a long animation, you should manually calculate a frame and ensure that the final effect is correct.

Tip: If your animation is just camera motion (such as an architectural tour effect map), you don't need to calculate the light energy transfer every frame, you just need to calculate one frame.