DAZ: Control of the simulation behavior

Pushee-Ri · 2023-10-23T08:13:22-04:00

While I'm stuck on a project again (no ideas for the promos - all the rest is done) here's a copy of one of my online "articles" (articles = small tutorials). It is about how to control the simulation behaviour of 3D clothing (or other objects) in DAZ via the surface parameters. Don't worry - it's not as technical as other descriptions! ---------------------------------------------------- In the real world, a cotton garment behaves like a cotton garment - regardless of the pose or position (undressed, discarded or only half-dressed). The garment always looks like the fabric it is made of. Unfortunately, this does not apply to the 3D world. A parameter-controlled 3D garment that looks good in one pose and position may behave strangely in another pose ... even if the parameters are the same. If you are interested in how the parameters work and how you can use them, below you will find some information about the most important parameters. To see the parameters, you should have a dForce object loaded. If the dForce object is selected in the "Scene" window, switch to the "Surface" window. You may also need to select the object in this window. After a long list of surface parameters, you will finally see the simulation parameters, starting with "Visible in simulation". This article is divided into two sections: 1. an attempt to describe the most important parameters and 2. some helpful parameter combinations. ----------------------------------- 1. the parameters Friction This parameter controls the way the fabric slips off the body. A low value leads to more slippage. Just think of silk (a lot of slippage - low value) and rubber (little slippage - high value). The Friction parameter - in combination with other parameters - is also very useful when you want a dForce object to stay in place. Self-collision The object should not only collide with another object, but also with itself. If you switch this off, the simulation time will be reduced ... but your simulated object will collide with itself. This does not look very realistic. Collision distance This parameter controls the desired distance between the dForce object and the model and also the self-collision distance. The default value is 0.2, but this value often results in a delayed simulation, as all vertices of an object that have a distance less than 0.2 (and there are usually many) are recalculated first. I usually use a value between 0.05 and 0.1 to avoid a long recalculation ... and also to avoid exploding knickers (see below). Dynamic strength The strength of gravity acting on the dForce object. The normal value is 1.0, but I like to use a value of 0.95 to avoid "over-impact" problems (like the exploding knickers mentioned earlier). Stretch Stiffness With this parameter you can control whether and how gravity can stretch (deform) the object. A high value results in less stretching / deformation. A low value in combination with the "contraction-expansion ratio" (see below) can be used to achieve really good results. Shear stiffness Like "expansion stiffness", this parameter controls the deformation of an object. This time the lateral slipping and twisting of an object is controlled. Bending stiffness This parameter allows you to control the amount and appearance of wrinkles and folds created during the simulation. Higher values result in larger wrinkles and shapes. To avoid simulation problems, I like to use a value of 0.25 instead of the normal value of 0.5. Kink stiffness This parameter controls the resistance of the object to compression. The normal value is 5.0, but I like to set it to 0.0 to avoid simulation problems. Kink stiffness Theoretically, higher values should behave like a light, flexible fabric, while lower values behave more like a hard, inflexible fabric. Density Controls the weight of the fabric. A low value represents a fabric like silk, a higher value represents a fabric like denim. This parameter (when set to a low value such as 30 or less) is useful for keeping objects in place during simulation. Contraction-Expansion Ratio This parameter controls whether the fabric shrinks (below 100%) or stretches (above 100%). Very useful for creating garments that shrink to fit or saggy/worn out garments. Parameter combinations As mentioned earlier, there is no universal combination. It all depends on the pose, the desired position, the inclination (gravity) and some other factors. The combinations listed here are therefore more examples that work best for upright models. "Shrink to Fit": Set the value for "Stretch Stiffness" to 0.20 - 0.40 (you can also reduce it further). The "Contraction Stretch Ratio" should have a value of 75% - 95%. If you wish, you can also reduce the "Shear Stiffness (Squares)". To keep the object in place, it is also useful to set the "friction" to 0.9 (or higher) and the "density" to a value of 80 or less. "Stay in place": Sometimes you want the 3D garment to keep its position (approximately). Obviously, it seems best to increase the value for "friction". However, this sometimes leads to "sticking" vertices and thus to garments with jags. Only in combination with some other settings does "friction" usually lead to good results. Friction" value: 0.8 - 1.0. "Dynamic Strength" value: 0.85 - 0.9. "Density (GSM)" value: 20 - 40. "More baggy / saggy": Even though the basic surface defaults result in a slightly baggy appearance, you may want to simulate garments with an even more baggy appearance. In this case, you can reduce the "Stretch Stiffness" to 0.20 - 0.40 and set the "Contraction Stretch Ratio" to 105% - 120%. -------------------------------------- Keep in mind: Change the settings only slightly! A too high (or too low) value sometimes leads to "exploding" 3D garments or - in the worst case - freezes the software. Caution - exploding knickers: https://www.renderhub.com/gallery/34244/caution-exploding-knickers Have fun experimenting!