如何在TracePro中模拟扩散片中英对照(附扩散片参数)

2020-05-07 21:07发布

如何在Tracepro中创建毛玻璃表面属性,设置扩散片


这篇文章将会告诉你在 tracepro 中,如何利用 ABg BSDF 模式创建一个漫透 射(例如,毛玻璃)。这种散射会有如下性质:

1) 散射的光线在空间呈钟形分布。

2) 大多数是透射,同时也有一部分是反射。

3) 反射光线的角度关系和透射光线一致。

4) 没有吸收。

5) 不存在镜面反射。 这种表面属性可以通过以下几个步骤来创建:

1) 用 excel 的电子表格来设置你所期望的 B 和 g 的值。增加 B 的值使得 钟形(贝尔形)的上端增大,并且增加 g 的值使得图形陡峭的部分变 得更加陡峭。在表格中,我们设置 A=B 来使得曲线正常化,标准化。

2) 假设总的反射系数,用菲涅尔反射系数来假设是个不错的选择,空气 中,玻璃的公式如下:

R =(n-1)2/(n+1)2


这里 n 为玻璃的折射率。如果你不知道玻璃的折射率,那么可以选择

R=0.05,这可以使的数值足够接近。其余的光线为透射光线,即:

1 − R

3) 在 tracepro 中打开表面属性编辑器,打开一个已经存在的表面属性,

并对其编辑,或者我们重新创建一个表面属性。

4) 设置吸收率为 0,

5) 设置镜面反射率等于 R 的值,

6) 在 BRDF 和 BTDF 中设置 B 和 g 的系数,其值就是你用表格得到的数 值,

7) 在 BRDF 和 BTDF 中设置 A 的值为 0,

8) 选择 BTDF 求解器,这会在保持 B 和 g 不变的情况下求解 A 的值,

9) 设置镜面反射系数为 0,

10) 选择 BRDF 求解器,

11) 保存,退出表面属性编辑器,

12) 你已经在毛玻璃设置这一领域炉火纯青,大师!

Translated by Daniel Lew

QQ:275435139

光行天下:amiferous

Haerbin china

2012-3-7



Making a ground glass surf ace property in TracePro


This note shows you how to make a transmitting diffuser (e.g. ground glass) for use in TracePro, using the ABg BSDF model. The diffuser will have the following properties:
1) Bell-shaped angular dependence of scattering.
2) Mostly transmitting, with some reflection.
3) Angular dependence of reflectively scattered light is the same as for transmissively scattered light.
4) No absorption.
5) No specular reflection.
The surface property can be created using the following sequence of steps.
1) Use the Excel spreadsheet DIFFUSER.XLS to determine the values of B and g that you desire. Increasing B makes the top of the bell wider, and increasing g makes the steep part of the bell steeper. In the spreadsheet we have set A=B in order to force the curve to be normalized, i.e., equal to one at zero degrees.
2) Guess at the total reflectance. A good guess is to use the Fresnel reflection coefficient, equal to

R =(n-1)2/(n+1)2


for glass used in air, where n is the index of refraction of the glass. If you don’t know the index, use R=0.05 and this should be close enough. The rest of the light is transmitted, or equal to 1-R.
3) In TracePro, open the Surface Property Editor and either open an existing surface property for editing (i.e. check the Edit Enable box) or create a new surface property.
4) Set the absorptance to zero.
5) Set the Specular Reflectance to R.
6) Set the B and g coefficients, for both the BRDF and BTDF, to the values you got using the spreadsheet.
7) Set the A coefficients to zero for both the BRDF and the BTDF.
8) Select Solve for: BTDF. This solves for A and leaves B and g unchanged.
9) Set the specular reflectance to zero.
10) Select Solve for: BRDF.
11) Exit the Surface Property Editor and save your changes.



DIFFUSER.XLS

赞赏支持