Conform modifier - collision proxy 快速產生碰撞體

在進行流體模擬時，使用的模型最好是封閉的(water-tight)的幾何體。但常常我們拿到的模型只是針對算圖好看，但卻很少是針對模擬所建模出來的，因此FX Artist必須花時間整理模型。

如果時間不夠的話這裡介紹一種快速方法 - Conform Modifier。

首先，先拉出一個能夠把鐵達尼號包起來的幾何體，以本例來說是Capsule

然後在Capsule上套用Conform Modifier，Method選Shrink Wrap，Direction選Closest point。這樣碰撞體就完成了，雖然不完美但是可以用在液體流體模擬上，簡單又快速。

[相關資訊]

Maxscript: Select By Measuring 根據體積來選取物件

Excire Foto - Aesthetics 圖片的美學等級與參數自動化

 

今天想來談談Excire Foto 這套德國圖片管理軟體。Exicre Foto有個很方便的功能就是會辨識圖片然後自動分類，它有預先設置好的關鍵字，例如Vehicle - Airplane...。這個軟體對我拿來整理參考圖時很方便。可以快速地撈到我要的reference。

Excire Foto還有另一個功能叫做sort by Aesthetics，根據美感來分類。聽起來很厲害對嗎?  其實這個Aesthetics的美感只能做到6-7成 (跟人類相比)，無法做到完全地自動化。

所以我這篇其實不是要講Excire Foto，我想說的是一家軟體功能要推出某某功能，如果真的像宣傳那樣好用，用英文來說就是"works as advertised"，那必然這套軟體會轟動，必定會大賣。

然而，絕大部分的情況，很多軟體公司宣傳的功能只能達到宣稱的6成，有些時候甚至完全沒用也是會發生的。說算圖不會閃爍，是絕對不會閃爍嗎? 是solid rock no flickering?說可以multi-thread，就真的所有功能都多線程嗎?

回到sort by Aesthetics這個功能來看，如果真的能做到，那不得了，可以做很多事。3D Artist很多情況是在不同版本間找到最好看的結果。如果軟體本身能判斷一張圖的Aesthetics，那麼就可以做到自動化，你可以產生100個版本，你可以用Phoenix FD跑不同的Dynamics設置，最終用軟體判斷哪個圖片好看，就可以達到自動化調整參數的能力。

或許以後，會出現某個按鈕 "Adjust parameters automatically"，等一個晚上或幾個小時，就得到你最想要的那個最佳化參數!

Phoenix FD with V-shape stern wake 船尾波的製作技巧

 

這篇要來分享一個之前有個客戶問的問題，就是遊艇後方的V-型波，或稱為stern wake。中文可以譯作船尾波。 一般船在航行時會產生兩個波，前方的叫做bow wave 船首波，後方叫船尾波。

預設的情況下，船首波很容易產生，把船的模型丟到場景裡，跑Phoenix FD Liquid sim，就自然會產生bow wave。要產生stern wake則需要多做一件事。

我們就不講背後的科學原理，直接講操作技巧。要在船後方螺旋槳的位置放一個box，然後從那個box噴出水。也就是說把那個box當成liquid source。

像這樣，因為這艘船是雙引擎，所以我放了兩個Box。選取那兩個面設置其face ID，使液體只從這兩個面噴出來。

這裡有個重點，就是那個box要稍微朝上，這樣液體射出時，會往上然後落下水面，會很自然地產生船尾波。

像這樣，就會產生你要的V-Shape stern wake。船尾波的形狀跟船速，船的大小還有船在水下的深度都有關係。

[相關影片]

Boat Wakes by McKellar Miscellany

Torque，RedefineFX tyflow VFX課程的建議

這篇我想來談談什麼是好的video tutorial。我就直說好了，能夠讓你在最短的時間內學到需要的技巧就是好的教學影片。甚至就目的性而言，我覺得重點在於提供場景檔，然後稍微解釋一下這個場景檔怎麼用，怎麼置換成你的模型(可能是一艘船或是一隻怪獸)，這樣就夠了。

不需要落落長的解釋所有細枝末節的東西，畢竟那些東西用戶自己慢慢消化就可以了。過度地想把所有的細節都解釋到，反而讓學生沒辦法學到關鍵的技巧。

我想舉的例子就是RedefineFX的Torque教學影片課程。這個教學很棒，用接近接案的實際範例來說明如何使用tyflow，講破碎，剛體，柔體，還有如何用Phoenix FD做煙霧爆破等。好萊塢式飛車追逐，直升機墜毀，很多技巧都有詳細說明。

但我想說的是，總時數太長了! 或許這是商業策略，好像讓購買課程的人會覺得俗又大碗，一大包的課程，有好幾小時可以學到所有技巧。

但如果你真的照個課程學習，你會發現很多部分是重複一樣的操作，一樣的技巧一再地講述。就當今的世界多種可以讓你分心的，資訊爆炸的時代，這樣做很難達到教學的效果。你講得再多，學生不見得都能，或是願意好好消化。

我覺得好的教學應該事先講大綱，然後操作點到為止，細枝末節不要講太多。當然，很多實戰的重點就在於修BUG，Torque這套課程裏面有很多部分在教你如何面對問題時要如何修正，這是很珍貴的。

我會更希望這樣的課程能濃縮這好幾個小時的教學影片濃縮到60-80分鐘，加上範例檔，會讓整個學習更有效率些。

[更多文章]

Tyflow - Surface Test (Distance) 根據距離觸發事件

Maxscript: Select By Measuring 根據體積來選取物件

這篇要介紹一個免費工具 叫做 Select By Measuring，作者是Vladislav Bodyul。可以到Scriptspot上免費下載這套工具。

安裝方式: 解壓縮後，把SelectByMeasuring這個macro script拖曳到3ds max的viewport中，就安裝好了。

但是你不知道介面在哪，請到Customize > Customize User Interface > Group: Main UI 在類別裡面找到 BodyulCG，然後自己創建新的UI Layer，把 BodyulCG的圖示拖曳過去，這樣就完成了介面。

怎麼用?

我們現在的目的是要把場景中太小的物體刪除。可以用Select by volume (根據體積來選取)，然後Condition設置Less Than(小於多少)。當然你會問我怎麼知道體積到底要設置為多少數值? 你可以先找到你認為合適的小零件，利用Fill from selection，這個工具就會根據該物件的體積或其他數值自動填入長寬高 或是體積。

然後再按下Select，就會根據條件選取場景中的零件。

這個工具很方便，很重要。尤其是當你要進行流體模擬時，比方說一艘船在海上航行。Hipoly的模型雖然算圖漂亮，但不適合直接拿來做流體模擬。需要整理一下模型，而像航空母艦這樣的通常有大量的零件，一個一個整理太慢。如果能事先刪出微小的零件，留下大的主要的幾何體那就方便了。這個工具讓你可以根據零件的體積或是bounding box的大小來選取，可以大幅加入工作流程。

[相關資訊]

3ds Max - Border Fill Maxscript補洞工具

Retopology in 3ds Max 教學影片筆記

Retopology in 3ds Max tips實際操作技巧

tyFlow v2 ZENITH what clients want 客戶要的是什麼?

 

tyFlow 2.0發表了，這次ZENITH增加了許多跟流體 (煙霧，火焰)有關的新功能。要恭喜背後努力開發的程式設計師，尤其是Svetlin。努力不懈地帶給3ds Max用戶以直以來夢想的功能。儘管目前還沒有液體，海洋等關於水的模擬功能，但相信不久的未來我們能看到夢想實現。軟體開發是一條辛苦的路，相信還會遇到各種問題，但這絕對是好的開始~

這篇要寫的不是軟體使用心得，我也還沒開始試用新的tyFlow。我想說的是，是廠商或是開發商要推出客戶要的東西，而不是問"客戶到底要什麼"，絕對不是顛倒過來。既然你是廠商或你要推出產品，你就必須要對市場有一定的認識，才會訂出軟體開發的方向。因此，只要看到軟體商推出問卷: 你認為下一版的軟體你最希望推出怎樣的功能時，我就會打從內心看不起該公司。難道客戶要什麼還需要你再問客戶嗎? 這幾年來，3ds Max用戶抱怨的bug，要求的新功能 - 比方說流體運算，每年都問，每年都要，廠商難道到不知道? 這些歷年來要求的功能都講到爛了~

只有那些新上台的，不專業，沒能力的c-levels主管才會推出問卷問客戶 "你們最想要什麼新功能"。我講白了，這只是顯示這些大頭主管的無能罷了，你們沒有能力領導，開發出客戶最想要的功能，才會裝傻推出那些問卷。

講白一點，客戶最想要的功能就在那裡，像一座山一樣，市場上所有的人都看得到。不要再裝傻了。一旦你真的推出一個客戶要的功能，而且這個功能沒有bug，是穩定的，絕對會有一大多人支持你。客戶就會口耳相傳買單。

還有客戶最想修好的bug，也是好幾年爛在那裡沒有修，爛好幾年了你還在裝不知道客戶到底要蛇小? 是把用戶當成白癡嗎?

V-Ray Graduated Filter 製作漸層天空的教學

這篇想來講講製作漸層天空的方法。像這樣如果你要渲染天空但是要有漸層感? 有玩單眼的應該會知道加一層漸層濾鏡就行。

那在V-Ray裡面要怎樣做呢? 很簡單。在場景中拉好 V-Ray Sun後，會自動在Enviromnet中添加V-Ray Sky的貼圖。這時候我們要做的是合成另外一張gradient map與vraysky合成。

合成是使用VRayCompTex。Source A是VRaySky，Source B是Gradient Ramp。

兩者是用相乘 A*B

D5 3.0 發表讓我對Chaos V-Ray近年來的發展更加失望

一直以來我都是推薦 V-Ray 以及 Chaos 相關的產品，但最近兩三年，Chaos 的表現卻每況愈下。看到 D5 Render 發表 3.0 版本的影片，只能嘆息一聲「恨鐵不成鋼」。

我知道 D5 Render是中國開發的軟體，因此我本身不會去使用，但就它的開發方向，我仍想談一點看法。很顯然，D5 Render 的許多功能都是針對建築視覺化所設計，強調直覺與方便，能夠非常快速地做出效果；相對之下，V-Ray 的功能層級更偏向底層，並非完全以建築為導向，因此在運用上更為靈活，能夠在非 AI 強化的情況下，透過細緻調整參數，逐步達到頂級擬真的算圖效果。

但 AI 已經改變了遊戲規則。很明顯，D5 已經開始侵蝕 V-Ray 原本稱霸的建築視覺化市場。過去的 D5 Render 還像是玩具一樣，只能產出「還算可用」的渲染圖；那麼 V-Ray 是否還能倚靠 VFX 市場站穩腳步？問題是，Chaos 有讓 Phoenix FD 這類特效相關軟體真正更加茁壯嗎？並沒有。原本可以成為 V-Ray 特色加分的功能，反而逐漸被邊緣化、被貶低。

再看近三年 Chaos 的開發方向：Chaos Envision 這套資產整合軟體（有點像獨立的 3D 軟體）、Chaos Arena 虛擬棚的即時渲染系統（坦白說，這和一般用戶幾乎沒有關係，誰家裡會有超大型螢幕來做虛擬攝影棚？），以及 Enscape 這套主打即時、快速的渲染軟體。這三個方向彼此之間幾乎沒有匯合感，Enscape 又在某種程度上與 V-Ray 形成競爭，而 Chaos Envision 與 Vantage 的定位也存在重疊。(好像漏掉了Corona)。整體來看，產品線繁多，但整合性卻相當差。問題是，客戶真的有錢到可以把你整條產品線一次買齊嗎？

用AI產生影像的技巧 - 讓人物產生特定的動作

 

為什麼有時候叫 AI 產生圖片，人物要做特定動作，比方說「頭轉向其左邊看」，結果 AI 都無法產生轉頭的人物？

因為 AI 並不是在讓模特兒轉頭，而是在從影像資料庫中拚湊一張「看起來合理的臉」。而「轉頭」這件事，對 AI 來說在機率空間裡反而是模糊、邏輯矛盾風險很高的。

對人類來說，叫人物頭轉左邊看，涉及三度空間與自我視角的概念；但對於 AI 生成影像來說，它看到的是「人臉」、「側臉」、「看某個方向」。AI 沒有身體座標的概念，所謂的「左轉」往往會轉換成鏡頭的左、畫面的左、角色的左。最後，AI 逼不得已只能產生邏輯上最安全的結果：給你一張正面的臉，或是一張側面的臉。

在 AI 的圖像資料庫裡，正面的臉最多，微側面也有，但是轉頭的、特定姿勢的卻很少。要產生正確的「頭轉一邊」，需要很多條件才能同時成立，例如眼睛、鼻子、嘴巴、頸部的肌肉等等；任何一項不吻合，就可能產生臉部融化、恐怖谷的現象。

聽起來有點反直覺：當我們給 AI 下越明確的指令，往往失敗率會越高。

• 漂亮的女性肖像，成功率高。
• 漂亮的女生「頭朝左邊轉頭看鏡頭」，成功率卻會變得爆低。

那麼，要怎樣才能產生特定動作的人物呢？

給 AI 下指令時，要關注於「畫面」，而非「動作」。描述鏡頭，而非人的主觀行為。你可以說「左側三分之四側臉」，或是「朝左的三分之四側面」，這樣成功率就會大幅提升。

有點麻煩，對嗎？其實這不是你的問題，這是整個世代的 AI 問題。這個侷限性是 AI 視覺空間的天花板，也就是 AI 本身的侷限性。

[相關資訊]

用AI產生影像的技巧 -模特兒的姿勢

Making realistic honey with Phoenix FD 蜂蜜流體特效

By Hammer Chen

In this article, I am going to share my tips & tricks for making realistic honey with Phoenix FD.

1. Modeling a honeycomb
Finding a photo-realistic model is very difficult. Even you have a budget to purchase from the online shop doesn't guaranty you get the right 3D model for the project. So I decided to model it by myself.

I found a handy tool from Scriptspot - Honeycomb, a maxscript by Anubis. This script allows you to generate a honeycomb shape with just one button.

Shading the Winter Explosion 冬季爆破特效

By Hammer Chen, Kristin Ivanova

We recently introduced the Artillery Explosion tutorial available in Phoenix FD’s documentation. Now, we want to show you a variation of this scene setup - a winter explosion with its proper shading.

This scene is essentially the same as the Artillery Explosion one, except for the smoke color and HDRI lighting. The smoke color is set to light gray in order to get a snowy look. To focus on the shading we also limit the number of bombs to just one.

Since there is a hot explosion at the core, it could make the rendering over-exposed or lose detail in the white smoke volumetric shading.

The good news is Phoenix FD provides a cohort of parameters allowing you to fine-tune the shading. Here we compare some of the useful settings that deal with this issue.

Overall Setup
The scene we use here is modified from the Artillery Explosion scene, except we add one Phoenix FD Turbulence helper and change the color of the smoke. For a step-by-step tutorial of how the Fire / Smoke sources and thinkingParticles are set up, please check out the Artillery Explosion tutorial.

Whitewater shading with Phoenix FD 白水效果

By Hammer Chen

Whitewater is formed in a rapid, when a river's gradient increases enough to generate so much turbulence that air is entrained into the water body, that is, it forms a bubbly or aerated and unstable current; the frothy water appears white. --- Wikipedia

In this article, I am going to show you how to set up whitewater shading with Phoenix FD.

To set up a scene for whitewater shading you will need:

1. A Phoenix FD Liquid Simulator - for simulation of liquid and generate "Vorticity smooth" data
2. A Phoenix FD Fire/Smoke Simulator - this is not for simulation. This Fire/Smoke Simulator doesn't have to be high resolution, because it purely functions as a container to load up "Vorticity smooth" data from Liquid Simulator, and shading / rendering them as smoke.
3. LiquidSrc

Large Scale Fire with Phoenix FD 大尺度火焰特效

 

By Hammer Chen, Kristin Ivanova

In the previous post, we saw how to create a small-scale fire. In this article we are talking about large-scale fires. A large-scale fire can be a ground fire, a wooden house on fire, or maybe fire in an explosion. Let's explore how to create realistic large-scale fire with Phoenix FD.

Fire is very tricky to make in CG. In the previous article, we have introduced the VRayDistanceTex to alleviate artifacts at the fire root. That is, by using a VRayDistance texture to modulate the fire opacity. In this article, we are going to give more tips & tricks for creating convincing fire.

First of all, let's talk about how the fire is emitted. Take a ground fire for example, we can use a simple plane (with shell modifier on top) and vertex paint to mask the fluid source. To avoid getting one big chunk of fire, paint the vertex color with smaller areas. This way we can create a more natural form of the flame.

Secondly, Phoenix FD Turbulence has a great effect on the overall motion of fire. For example, below we compare the dynamics of a flame without Phoenix FD Turbulence and with Phoenix FD Turbulence. See how the flame looks dull without Turbulence.

Making of Lava Flow with TexUVW 岩漿特效

 

By Hammer Chen, Kristin Ivanova

Phoenix FD 4's new feature TexUVW opens a great opportunity for adding details to your fluids. It allows fluids to transport UVW information along with the moving fluid. You can find an example in the "Using TexUVW for Creating Thin Smoke" tutorial, available on the Phoenix FD official page. In the tutorial, smoke opacity is masked with a noise texture, with the help of TexUVW, to enhance the details that mimic thin smoke. 

In this article, we are taking advantage of this new feature in order to create a lava flow. The folding character of the lava is generated through bump maps and displacement.

References

When creating a lava stream, we need to consider what type of lava we want to use for reference. A variety of lava types exist depending on terrain, speed, hotness, and material composition. For the purpose of this article, we will create a "pahoehoe"  (pronounced 'paw-hoey-hoey") type of lava (see the reference images above), which creates folds as it moves. However, if you intend to simulate molten lava, you can check the "Solidifying of Molten Lava" tutorial on the official documentation site.

Making of Deer Crossing River 麋鹿渡河特效

By Hammer Chen

In this article, I am going to share some tips & tricks of how I made this deer crossing river animation. Although it might look daunting at first glance, the settings for Phoenix are quite simple. The most critical thing for making this animation is the hardware.

As you can see, the total cache size for the whole animation (250 frames) is around 535 GB. So you better have a faster RAM and a hard drive with enough space for this kind of project. Once you have your hardware ready, leave it to Phoenix, Don't worry, Phoenix FD does support large-scale fluids like this one.

The image above shows my scene setup. The herd of deer is generated from a single rigged deer, duplicated by using thinkingParticles. There is no animation variation of the deer character, so the setting is simple, only offsetting animation for each deer.

VRayVolumeGrid and Nuclear Explosion 核爆整合

By Hammer Chen

In this article I am going to show you the benefit of using Phoenix FD in tandem with VRayVolumeGrid. I will use a nuclear explosion as an example.

Phoenix FD is capable of simulating complex explosions, such as air strike, small or large scale explosion. For a realistic blast, it always involves many different components. For example, the nuclear explosion you have a major mushroom cloud that flies into the sky; and the ground dust triggered by the mushroom cloud explosion. With multiple fire/smoke sources, Phoenix FD can perform realistic nuclear explosion simulation. In fact, you can find a downloadable nuclear explosion scene on the ChaosGroup official sample page.

With that said, what if you want extra degree of freedoms for tweaking and shaping the extract nuke you want. Simulating each component separately might be a way to go. I'll explain why.

A collection of reference images from the Internet

Let’s take a look at physical reality. A nuclear bomb was placed on the ground, somewhere in an unknown desert. When the bomb blast off, initiate the chain reaction, heat climbing and generate lots of smoke as a by-product the chemical reaction; that major explosion pushes the ground dust which is already there before the blast. We can say the physical properties of those two elements (the ground dust and explosive mushroom) are no doubt different things.

Bullet Time with Phoenix FD 子彈時間慢動作特效

By Hammer Chen

Have you ever wondered how to create a bullet-time effect for liquids with Phoenix FD? Especially when working with rigid body simulation? The answer is surprisingly simple: animate the Phoenix FD's "Time Scale" parameter. In this article, I am going to show you the workflow.

1. Scene Setup

We have two wine glasses in the scene  and a sphere flying from right to left, that hits and breaks the glasses. You can use any package to simulate the rigid body dynamics, for example,  PFlow mParticles or RayFire. In this case, I use thinkingParticles.

Visualize your forces with Force Preview 視覺化力場

by Hammer Chen

When dealing with complex scene, sometimes you have to adjust forces in the scene back and forth to get the desired results. You have to change parameters, run the sim, render preview and change parameters again.

For creating ocean maelstrom, adding a vortex force might be a quick answer. However, finding the right parameters could be a nightmare for you. If the orbital speed too high, or it's falloff too short. Or if there is not enough radial pull. You might not be able to get the right maelstrom.

With new Force Preview, you can see how Phoenix or standard 3ds Max forces will influence the simulation — without multiple iterations

Making of a Burning Motorcycle 燃燒的摩托車

By Hammer Chen

In this article, I am going to show you some of the critical steps of making this burning motorcycle image with Phoenix FD.

The model was kindly provided by Lien Ying-Te. Though this is a sub-D model, there are a lot of parts and faces in the geometry. The first thing I do is attach all the pieces into one single mesh, and then use ProOptimizer to reduce the polyfaces to roughly 10% of its original polycounts. You get a significant simulation performance increase when you have fewer polycounts as a fire/smoke source.

Making clouds with Phoenix FD 雲朵模擬教學

by Hammer Chen

Do you know you can create realistic cloud by simply budding off smoke from a single plane? The key is using the right mask and scattering setting.

Here we have one 3dsMax plane primitive as Fire / Smoke source. (Please note that Phoenix FD doesn't like non-closed geometry. If you having any trouble emitting fluid from a plane, add a shell modifier to the plane can fix the issue)