4.3 Mesh Orientation vs. Rotational Force【網(wǎng)格體朝向和旋轉(zhuǎn)力的對比】

總結(jié)：

1：直接設(shè)置類型：Initial Mesh Orientation【初始網(wǎng)格體朝向】模組、Update Mesh Orientation【更新網(wǎng)格體朝向】模組，直接設(shè)置朝向，不受其他力或速度的影響，低性能消耗。

2：施加力類型：Mesh Rotation Force【網(wǎng)格體旋轉(zhuǎn)力】模組、Drag【阻力】模組里的旋轉(zhuǎn)阻力，用接近現(xiàn)實的物理方法來計算旋轉(zhuǎn)，受網(wǎng)格體尺寸和質(zhì)量影響，高性能消耗

3：施加速度類型：Add Rotational Velocity【添加旋轉(zhuǎn)速度】模組，添加的旋轉(zhuǎn)速度疊加到原本的旋轉(zhuǎn)速度中，疊加時不受網(wǎng)格體尺寸和質(zhì)量影響，之后則會受到力和其他疊加旋轉(zhuǎn)速度的影響，中性能消耗

Calculate Size and Rotational Inertia by Mass【計算大小和使用質(zhì)量計算轉(zhuǎn)動慣量】模組：通過尺寸計算大小，并使用密度計算質(zhì)量，最后計算轉(zhuǎn)動慣量

Calculate Mesh Scale【計算網(wǎng)格體比例】：為True時，模組計算結(jié)果寫入Particles.Scale，為False時，模組計算結(jié)果寫入Particles.SpriteSize。

（僅Calculate Mesh Scale為True）Initial Model Dimension【初始模型尺寸】：即網(wǎng)格體尺寸(Approx Size)

Manually Entered Density(kg/m^3)【手動輸入密度】

Density by Material Type【通過材料類型獲得密度】

Rock【石頭】

Steel【鋼鐵】

Wood【木頭】

Water【水】

Paper【紙】

Styrofoam【泡沫塑料】

Mass Modulation【質(zhì)量調(diào)整】：質(zhì)量乘數(shù)

（僅Calculate Mesh Scale為True）Model Proportions【模型比例】：影響質(zhì)量在網(wǎng)格體各軸的分布

（僅Calculate Mesh Scale為False）Width【寬】：影響質(zhì)量在圖片 X軸的分布

（僅Calculate Mesh Scale為False）Height【高】：影響質(zhì)量在圖片 Y軸的分布

（僅Calculate Mesh Scale為False）Depth【深】：影響質(zhì)量在圖片 Z軸的分布

Mesh Rotation Force【網(wǎng)格體旋轉(zhuǎn)力】模組

Rotation【旋轉(zhuǎn)】：設(shè)置施加到各軸的旋轉(zhuǎn)牛頓力

Coordinate Space【坐標空間】

Apply Initial Forces【應(yīng)用初始化力】模組：把初始力轉(zhuǎn)換為初始速度

Apply Force to Velocity【應(yīng)用力到速度】

Apply Rotational Force to Rotational Velocity【應(yīng)用旋轉(zhuǎn)力到旋轉(zhuǎn)速度】

Apply Fore to Position【應(yīng)用力到位置】

（僅Apply Fore to Position）Position Force Warmup Time【位置力熱身時間】：物理力對位置影響的作用時間

Add Rotational Velocity【添加旋轉(zhuǎn)速度】模組：添加旋轉(zhuǎn)速度并疊加到原本的旋轉(zhuǎn)速度中

Rotation Rate【旋轉(zhuǎn)速度】

Coordinate Space【坐標空間】

Direct Orientation Modules (Initial Mesh Orientation, Update Mesh Orientation) Use a "direct set" approach to the orientation of mesh emitters. They directly assign an orientation value which creates a constant rotation rate irrespective of the size or mass of the mesh particles.

Notice in this example the particles always rotate at the same constant speed regardless of size/mass. Think of it as a constant "rotation rate".

This is an inexpensive approach and gives users direct control over rotation based on particle age or other metrics.

In this model, rotational drag (an option on the drag module) has no effect.

【直接設(shè)置朝向的模組（初始網(wǎng)格體朝向模組，更新網(wǎng)格體朝向模組）使用一種“直接設(shè)置”的方法來設(shè)置網(wǎng)格體的朝向。它們直接分配一個朝向值，從而創(chuàng)建一個恒定的旋轉(zhuǎn)速率而不管網(wǎng)格體粒子的大小或質(zhì)量是多少】

【留意這個示例中粒子總是以相同的恒定速度旋轉(zhuǎn)而不管它的大小或質(zhì)量。可以認為它是一個恒定的“旋轉(zhuǎn)速率”。】

【這是一種低性能消耗的方法并給用戶直接根據(jù)粒子壽命或其他指標控制旋轉(zhuǎn)。】

【在這個模型中，旋轉(zhuǎn)阻力（在拖拽力模組里的選項）是無效的】

Mesh Rotational Force modules are a force based rotational system which deals with a more physical approach to rotations. "Mesh Rotation Force" and "Drag", combine to create a force based model where Mass and Rotational Inertia are factored into the final rotation values.

This model relies on Mass being set per particle, then we derive a mesh scale from that mass value by using the "Calculate Size by Mass" module suite. Notice this model requires "Initial Model Dimensions" to be set, this is the size of the mesh, as imported in cm, and can be found by hovering over a mesh thumbnail in the content browser.

We still directly set an initial orientation in spawn, but in update we apply a force, and rotational drag, and then we allow those to integrate using a special solver.

Notice in this model, large meshes rotate more slowly as they have higher rotational inertia, drag has an effect on the speed of rotation, and so on.

This model is a bit more expensive but can create desirable results in the case where you want larger particles to respond more realistically to stimulus.

【網(wǎng)格體旋轉(zhuǎn)力模組是一個基于旋轉(zhuǎn)系統(tǒng)的力，這系統(tǒng)更多是以物理方式處理旋轉(zhuǎn)?！熬W(wǎng)格體旋轉(zhuǎn)力”模組和“拖拽力”模組，結(jié)合起來形成合力并基于受質(zhì)量和轉(zhuǎn)動慣量影響的模型來形成最終旋轉(zhuǎn)值】

【這個模型依賴于每個粒子的質(zhì)量，然后我們通過使用“計算大小和使用質(zhì)量計算轉(zhuǎn)動慣量”模組從質(zhì)量數(shù)值獲得一個適合的網(wǎng)格體比例。注意此模組需要設(shè)置“初始的模型尺寸”，這是網(wǎng)格體的尺寸，單位為厘米，這尺寸可通過鼠標懸停在內(nèi)容瀏覽器的網(wǎng)格體縮略圖上獲得。】

【我們?nèi)匀辉谏蓵r直接設(shè)置一個初始的朝向，但在粒子更新階段應(yīng)用一個力，以及旋轉(zhuǎn)阻力，然后我們允許它們使用特殊計算合并在一起】

【留意此模型，大網(wǎng)格體因為有更高的轉(zhuǎn)動慣量而旋轉(zhuǎn)變慢，阻力也能影響旋轉(zhuǎn)速度，等等】

【這模型消耗更多性能但可以創(chuàng)造出需要的結(jié)果，比如當你需要讓更大的粒子反應(yīng)得更接近現(xiàn)實的情況】

Rotational Forces accumulate into a Particles.RotationalVelocity variable and persist from frame to frame. Here we give the particles an initial "kick", by applying a Rotational Force and then applying those forces to the Rotational Velocity. We use this method as it factors mass into the initial rotational velocity.

This then gets solved by the solver in update, and rotational? drag eventually slows the particles down.

If you want the initial "kick" to not factor in mass, you can use an "Add Rotational Velocity Module" to directy set a rotation speed in particle spawn.

【旋轉(zhuǎn)力積累進Particles.RotationalVelocity變量并能保持到下一幀。這里我們給粒子一個初始的“一腳”，通過施加旋轉(zhuǎn)力然后應(yīng)用這個力到旋轉(zhuǎn)速度。我們使用這種方法使質(zhì)量影響初始旋轉(zhuǎn)速度】

【這在更新時被結(jié)算器結(jié)算，旋轉(zhuǎn)阻力最終使粒子變慢】

【如果你想這初始的“一腳”不受質(zhì)量影響，你可以使用“添加旋轉(zhuǎn)速度”模組來直接在粒子生成階段設(shè)置旋轉(zhuǎn)速度】

As a fun little trick, we assign RotationalVelocity to the "Find Kinetic and Potential Energy" module (under advanced options) which returns us an output we can use to drive the emissive value of the Mesh Particle material. The faster the mesh spins, the brighter it gets.

【作為一個有趣的小技巧，我們安排旋轉(zhuǎn)速度到“獲得動能和勢能”模組（在高級選擇中），并用輸出來驅(qū)動網(wǎng)格體材質(zhì)的自發(fā)光值。網(wǎng)格體轉(zhuǎn)得越快，網(wǎng)格體越亮】