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Collision Detection

For some time Poser has had a simple form of collision detection built in. Its main limit is that Poser has no physics system built in, so you have to move things yourself to see if they collide, but it can still be a useful tool for posing. In particular, it can be a very quick way of making sure that a shoe is touching a surface, or a hand a wall, without having to repeatedly render test scenes.

You will find the basic control for this feature on the properties panel for every prop and body part in your scene (including the ground).

Fig 3: Collision Detection settings
Fig 1: Collision Detection settings

You can turn collision detection on or off for each object or body part in your scene. In addition, you can apply the settings for one part of a figure to all of its children. This can be very useful when you are trying to pose a hand - select the hand itself, turn on Collision detection and click on the Apply Collision Settings to Children button, and all of the fingers and the thumb will also use collision detection. The same works for feet and toes.

Be careful not to apply collision detection to too many parts of your scene at once - having an entire figure using collision detection can radically slow down your computer and make posing almost impossible.

Fig 4: Collision Detection options
Fig 2: Collision Detection options

The Collision Detection options can only be found on the context menu for the preview window (the small triangle at the top right of the window, hidden behind the menu itself in Figure 2). There are three options for Collisions - On, Off and Show intersections. On and Off work as you would expect - turn collision detection on, and items that are set to detect collisions can not be moved through each other.

Show intersections is perhaps the most interesting use of this feature. In many cases, you will actually want a slight overlap between two objects - when getting a grip right for instance, or in the case of Figure 3 when getting a foot to look like it is actually on a surface. In this case, if we simply use Collision detection turned on, the foot will look like it is floating very slightly above the step, as the base of the foot is not entirely flat, and Poser models have no 'give' in them (unless we add it ourselves). Instead, we can use Show Intersections to move the foot until it is just in contact with the step.

Fig 5: One foot in place
Fig 3: One foot in place

Figure Three shows what happens when two objects with collision detection turned on touch while Show Intersections is turned on. Every object that has collision detection turned on turns gray. When two objects with collision detection collide, the polygons that touch all light up in red. If you are wondering why not of the shoe is lit up, the polygons that are touching the step are on the base of the shoe, and thus hidden from view. If you move the shoe too far polygons on the side also start to light up.

To get the best results out of this, I recommend turning IK on for the foot or hand in question, and then using the dials to move it gently in the right direction. This allows you to make very precise movements until you are entirely happy with the results (when you turn IK off, the feet loose their translation dials).

Fig 6: Two collisions at once
Fig 4: Two collisions at once

Figure Four shows that one object can collide with several different parts of the same object. One thing to bear in mind with collision detection is that it shows you what objects your currently selected prop or body part is touching. When you swap to another body part, the original collisions disappear. If you want to see where both feet collide with the steps, you would need to select the steps instead. This can be very important when getting a grip right.

Fig 7: Accurate Shadows
Fig 5: Accurate Shadows

Figure Five shows the result of using collision detection to pose the feet. Here, sharp ray traced shadows show that the two feet are indeed in contact with the steps. The same could be done to make sure a hand is just touching a wall.


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