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Author Topic: LUMION 5: How to reduce render times  (Read 66960 times)

LUMION 5: How to reduce render times
« on: July 11, 2012, 12:04:59 pm »
July 11, 2012, 12:04:59 pm
Render times in Lumion 5 are primarily affected by the following factors:

1) Your graphics card
This is the single most important factor that determines how fast you're able to render each frame. Please read this post to find out if you might benefit from upgrading your graphics card.

If you do decide to invest in a faster graphics card, please double-check that the graphics card is compatible with your PC and that the power supply in your PC is capable of providing sufficient Wattage.

The final rendered image will be virtually identical regardless of which graphics card you're rendering videos/images with (subject to driver versions and settings), provided that the card meets the minimum requirements.

Generally speaking, the speed of the card affects performance in Build and Movie mode (measured in frames per second) as well as render times. The onboard memory of the graphics card will limit the complexity of your scene (Number of polygons and texture numbers/amounts).

Also bear in mind that the CPU is not used much while rendering still images and videos - it's mainly used for compressing frames after they have been rendered.

2) Graphics card memory
Windows 8.x and 10 do not allow DirectX 9 applications (such as Lumion 5.x) to use more than 4GB graphics card memory for a given application. However, in Windows 7 this cap does not exist. The developers are aware of this problem and are researching possible solutions (Nvidia has confirmed to one of our developers that they have also replicated the problem - hopefully this can put some more pressure on Microsoft to resolve the problem).

For the time being we recommend that you use Lumion in Windows 7 if your graphics card has more than 4GB memory, so that you can take advantage of all of the available graphics card memory. You can of course still use Lumion on Windows 8.x and 10 if your graphics card has more than 4GB memory, but you will just not be able to use any graphics card memory above 4GB.

If your graphics card has got 4GB memory or less, you can use Lumion on Windows 8.x and 10 without noticing the memory problem (according to those of our users who have already upgraded to Windows 10 Beta).

3) System memory
System memory (RAM) is used in Windows 7 if your graphics card runs out of memory when rendering complex scenes in Lumion. Lumion can't use system memory in Windows 8.x and 10. System memory is significantly slower than graphics card memory and can make render times longer.

4) The complexity of your scene
Complexity refers to the number of polygons in your scene and how many different textures that are used. Bear in mind that a scene with 100 different models/materials will render slower than a scene with 100 identical models, so if render times are important, avoid using many different models from the Model Library. You should also consider hiding models that are obstructed behind other models via the Layer functionality.

The number of vertices in your scene also has a big impact on render times. A model consists of triangles, and each triangle consists of 3 3D Points. The lower this number is, the faster your render times will be. Here's how to find out how many vertices there are in your scene:

1) Zoom out so everything is in view.
2) Press F7 to render the terrain at the maximum level of detail.
3) Press F9 to render the trees/plants are rendered at their maximum level of detail.
4) Check how many "3D Points" your scene has in the top right corner. 500k means 500,000 3D Points.

5) Spotlights with dynamic shadows
When you add spotlights to your scene, their shadows are not updated dynamically by default.

In Lumion 3.0.2 and later versions, you can choose whether to use dynamic or static shadows to improve performance and reduce render times.

However, every time you switch to dynamic shadows for a spotlight, the entire scene has to be rendered once more. Add 10 spotlights with dynamic shadows and the scene has to be rendered 10 times more every frame.

If you use the Global Illumination, each spotlight causes the scene to be rendered once more per frame, regardless of whether the spotlight is using dynamic or static shadows.

In Light Properties -> Optimize for, choose what is most important for each light:

  • Accuracy: The shadows are updated every frame (Slow!). Every time you add a light with Accuracy turned on, the entire scene has to be rendered once more. Add 10 lights and the scene has to be rendered 10 times more every frame. Each light uses a 2048x2048 pixel shadow texture.
  • Memory: The shadow from the light uses a static 128x128 pixel texture which is not updated (Fast, very low memory usage)
  • Speed: The shadow from the light uses a static 512x512 pixel texture which is not updated (Fast, moderate memory usage)
To reduce render times, we recommend that distant lights (e.g. street lights) in your scene use either the Memory or the Speed option, so that the shadows are not updated every frame. If your graphics card has enough memory, the best option is Speed.

We recommend that you should only ever choose Accuracy for your lights if:

  • Something that casts shadows is moving near the light (a car driving past a street light for example).
  • The light itself moves/rotates (stage lighting for concerts for example).
  • You need high-resolution shadows in certain areas (typically close-ups of interiors).
5) Planar reflections
Planar reflections are available via the Reflection effect in Movie and Photo mode (New effect -> World -> Reflection).

This Movie effect allows you to specify up to 10 reflection planes in your scene. Any model surface which is co-planar with a specified reflection plane in your scene will have accurate reflections. This is ideal for mirrors, marble floors etc. The effect includes a Threshold slider which allows you to adjust the distance at which nearly-co-planar surfaces will be included in the reflection plane. The tradeoff is accuracy but it's usually not noticeable. Please note that if you have some nearly co-planar surfaces that you want to assign a single reflection plane to, you need to assign the plane to the surface which is closest to the camera so to speak.

Every time you add 1 reflection plane, Lumion has to mirror all models and render the entire scene once more. For that reason, try to use as few reflection planes as possible.

  • Restart Lumion before you start rendering very complex scenes; this will minimise memory consumption, and may improve render times in some situations.
  • Turn on "Limit all texture sizes to 512x512" in the Settings menu to reduce the resolution of the textures in your scene; this will minimise memory consumption, and may improve render times in some situations.
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