The Essential Thinking of Roughness and Anisotropy (5)

In this article, we first learn the principle of directly creating an anisotropy rotation map by bypassing the flowmap. Since the flowmap is not so intuitive, it cannot be used directly in some renderers (vray, redshift). We can start by trying to make an anisotropy rotation map directly.
The tool used is of course the program texture overlord - the substance designer.
First of all, we have to clarify the goal, know exactly what the texture effect to achieve, and then want to make a plan. Now let's analyze what features have been verified and feasible.
We will re-combine the pixel process node in SD before, use -0.25 instead of -0.25, this will make the final output picture brightness completely within the range of [0,1], so that we can observe the picture characteristics. (The only meaning of this operation is for good observation).

Now the picture looks like this, it shines a lot. All brightness is between 0, 1.

At this time, we use a node called histogram select in SD to observe the picture, so we can see how the scratches of different brightness in the picture are distributed.
The figure below shows the effect of sweeping the original image from 0-1.

Here we can find two characteristics of this picture:
Carefully staring at one end of a line, you will find that the line has rotated 360 degrees completely in the process.
Under the same color gradation, the direction of the scratch is basically uniform.
Why can such a feature create a ring-like scratch? This is related to the attributes on our shader.
The material sphere has an anisotropy rotation property that specifically controls the direction of rotation of the opposite sex highlights. The input range of this attribute is 0,1, and the value has a corresponding relationship with the angle:
0 : 0°
0.25 : 90°
0.5 : 180°
0.75 : 270°
1.00 : 360°
The middle is the linear difference, and you should understand this parameter very easily.
The figure below shows the effect of anisotropy rotation changing from 0 to 1. The highlight is turned 360 degrees:

So in fact, we only need to make a scratch map that meets these two characteristics to achieve the goal:
The brightness of each scratch changes with the angle
The same angle of scratch brightness is the same
This is shown by the diagram (rotate 0 = rotate 1)

After knowing the principles and goals, we have to find a way to achieve this, a simple implementation in Substance Designer.
This one we only want to talk about ideas, because friends who will use SD software should be in very few.
However, if you already understand the above ideas, you can do it in theory with ps, but it is quite a lot of trouble.
Node graph is relatively simple.

The main thing is to use the tile sampler to do the scattering, the shape node is a square, pressed very flat to make scratch elements. A Gaussian noise makes the spread random.
This gaussian noise should control the rotation and brightness of the scratch at the same time. The final effect is that the darker the gaussian noise is, the smaller the rotation angle is, and the lower the scratch brightness is.
The resulting aniRotation texture effect, SD is naturally seamless.

Then use the histgram select node to check the effect, because we are using a black background, so when the brightness is 0, the large area of the screen is selected, this does not matter, the overall effect looks the same as we expected:

Because this is the simplest implementation, this scratch is not a fancy thing, it is straight. The core principle is the content described above.

Interested

The Essential Thinking Of Roughness And Anisotropy (2)
The Essential Thinking Of Roughness And Anisotropy (2)
As a leading cloud rendering service provider, we are also a Redshift render farm, we published an article about “The Essential Thinking Of Roughness And Anisotropy (1)” last week. However, If you follow the view, you will find that you don't need the roughness parameter at all. The rougher the reflection, the better the texture with a higher bump strength is solved, let’s continue to discuss the roughness and anisotropy. In theory, this statement is correct, and it is also very physical and in line with people's real life experience. But this kind of practice of using roughness to make roughness, there is a professional word to describe him, everyone who plays rendering should be familiar with it - brute force The reason is the same. This way, when you render GI, use the brute force algorithm to mean that the microstructure you express may be very accurate, but the rendering speed is extremely slow. maxAA = 4 maxAA = 117 maxAA = 1024 maxAA = 8192 As can be seen from this set of graphs, when the roughness parameter is used to adjust the reflection roughness, there is no noise at very low sampling. But with bump control, very high sampling is required to effectively reduce noise. And even if the sample is given to the system with a maximum value of 8192 (the pictures are rendered using the Redshift renderer, the sample unit of rs is the square of the value of the sample equivalent to subdivs, where 8192samples is equivalent to about 90 of the subdivs; In addition, using maxAA to improve quality rather than using lighting samples is because the noise is not caused by insufficient light sampling, but the texture is very fine and must be super-photocamera to sample, and still see obvious noise. That is to say, this idea is only theoretically correct, but it is a big mistake in production and industrial processes. Then the roughness parameter was introduced to solve the problem discussed above.
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2019-04-01
How the Redshift Proxy Renders the Subdivision
How the Redshift Proxy Renders the Subdivision
I think this question should be a very common problem and a problem that is often encountered in movie animation projects, so I am going to write a tutorial on subdivision today. Everyone knows that in the Maya scene, if you want to create a proxy, you must first export and then create it. Then let's first talk about the Export Proxy: Redshift - Proxy - Export, be sure to click on the small box behind the Export. Then, keep the General Options - File Type - Select Redshift Proxy in default, meaning that this proxy is a Redshift proxy. The next step is the important what we need to know: File Type Specific Options – General, and there is an Export Polygon Connectivity Data under General. What does this option mean? The official Redshift documentation explains this: The Export Polygon Connectivity Data option should be used if you plan on applying any tessellation & displacement to the proxy. Enabling this option does increase the size of the proxy file, so should only be used if necessary. In other words, if you want the Tessellation and Displacement options under the properties of your proxy to work, you must check the Export Polygon Connectivity Data option when exporting the proxy, otherwise, no matter what proxy file will be set, there is no subdivision or permutation in the proxy model. Except for one case, you have already set up all the model substitutions and subdivisions before exporting the proxy. Replacement I can guarantee that all projects are set up, but the subdivision is not necessarily true. For now, you can know that why I want to export the proxy, because this is the key to whether the redshift proxy can render the subdivision. And the last command is below: Sequence -Export Sequence, it's easy to know, export the animation sequence. After finishing the proxy export, now say about Create Proxy: Redshift - Proxy – Create. After the creation, put the proxy file you exported into it. Under your proxy properties, check Overrides - Tessellation & Displacement. Then find the Redshift Proxy Placeholder Shape panel property Redshift - Tessellation - Enable, check Enable is OK, as for the subdivision parameters, according to your needs to modify it yourself.
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2018-12-28
Say Goodbye To Model Chamfering, Introduce Roundcorners To You
Say Goodbye To Model Chamfering, Introduce Roundcorners To You
The demos in the article are all based on the Redshift 2.623 postFX special version renderer, but other mainstream renderers (Arnold, v-ray, etc.) have similar functions. Arnold needs to be in the latest version, which is a recent new feature. It is available during the use of MtoA3.1.1 Arnold Core 5.2.1.0. 1) Basic introduction of RoundCorners technology The round corners technology was first used in the mental ray era, which was before 2010. This means that the technology itself is very old. However, it rarely appears in various rendering tutorials, so the penetration rate is quite low. Recent test results show that this technology can be very useful in many cases and is a technology that is seriously underestimated. Its main functions are divided into two pieces: 1. let the original hard edge produce a smooth chamfer effect. 2. Make natural overgrowth at the junction of the two intersecting objects. The specific way to do this is to create a RoundCorners node and connect the output to the bump input of rsMaterial to create an edge chamfer effect. The Radius value controls the size of the chamfer. If you do not check the Consider Same Object Only, it means that all objects with this material will have a chamfer effect, and a blending chamfer effect will be formed between different objects, that is, the effect of Figure 3. If the "Consider Same Object Only" is checked, it means that there is no chamfer effect between different objects, that is, the effect of Figure 2. Because round corners will take up the bump input, if the material itself has a bump, then the bump blending technique is needed. Create a bump blender node, mix the process bumps, and check the additive mode to get the perfect overlay effect. 2) The principle of producing good-looking highlights When making the model, everyone knows that the model needs to be chamfered and cannot have a hard edge. Perhaps the explanation you have heard is that objects in real life cannot be so sharp, there are always some rounded arcs, the difference is only the size of this arc. 、 This statement is of course correct, but it is not a conclusion drawn from the perspective of rendering. As shown in the figure below, the reflection area of a square box without chamfering is shown, and the dark diagonal line marks the approximate reflection area. The green area is marked with words, which is a reflection blind zone. It means that when the light is in this "reflection blind zone", the model can't observe the highlights. At this time, the model texture looks very much like lambert! This is a very bad phenomenon. If the model is chamfered, then this reflection dead zone will not exist, and all the lights in the "original reflection blind zone" will form a slender and beautiful highlight on the chamfer. This will give a good representation of the texture of the material. (The reflection area of the chamfer will be very large, and it is easy to form a high light. It is easy to observe the phenomenon around it.) [1] The difference between chamfering or not, the contrast between the two figures is perfectly reflected once again. Note the image below, where the highlights appear, basically in the chamfered area. This section mainly explains the principle and flaws of forming a good-looking highlight. The specific solution is to chamfer the model, or the cheaper and convenient method is the RoundCorners technology introduced in the article. 3) Limitations of RoundCorners technology The chamfering effect produced by RoundCorners is generated by bump. It also achieves the effect by changing the normal direction of the surface of the model, but does not change the structure of the model itself. So when the angle of observation turns to some cases, the area of the chamfer becomes When the outline of the model is observed, an abnormal visual effect is observed. Think about it, RoundCorners' chamfer is equivalent to shrinking these hard cut corners in a circle. This is a visual change; however, the real model is actually unchanged, so the conflict between the two forms. Incorrect visual effects. Some people may have thought that they can try to solve this problem by using the RoundCorners node as a replacement. Unfortunately, both the arnold and redshift renderers are not. At present, this problem cannot be solved temporarily. This technology is very convenient. To be clear, we use RoundCorners to form very small chamfers. When the chamfer is small, it is difficult to observe the problems described in this section. We can apply this technique to the mid-range and perspective of rendering. Very close-up close-ups are still used to achieve super high precision using model chamfering. Or when the required chamfer curvature is relatively large, it needs to be directly made on the model. 4) RoundCorners response to permutation Because there are a lot of situations in which the replacement is used in the film and television rendering, I also carried out the relevant test of the replacement, and the effect is satisfactory. The rendering of the following three images uses two patches, one of which uses a black and white checkerboard for replacement and the other with a water surface. And use the RoundCorners node to control the tension between the water surface and the wall to form a curved arc. The final result can be seen, is successful, RoundCorners responded very well to the displacement effect. In the three figures, the radius values of the RoundCorners node are 0, 0.02, and 0.1 respectively. It can be seen that 0 and 0.02 produce an essential difference in the high gloss of the contact surface. It is exactly the same as the content explained in the previous article. The effect of 0.1 is actually wrong. It can be seen that the amount of curvature generated by the water surface is obviously too large, but this is more likely to have a high light effect. Radius = 0 Radius = 0.02 Radius = 0.1 Model screenshot 5) RoundCorners practical application (with scanning material) Finally, with the application of the scanning material, the effect here is closer to the actual production application in the project. What quality effect RoundCorners can achieve. A B C Reference: Daiwei
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2019-03-29
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