What is Light Samples Multiplier - LSM?


Number of direct lighting samples per each GI sample. Increase this value in scenes with visible noise in direct lighting. Default value of 2.0 works well in most cases.



You can find the Light Samples Multiplier parameter in:


3ds Max:

Render setup > Performance > Performance Settings




Cinema 4D:

Render Settings > Corona > Performance Settings > Sampling Balance section:



It multiplies the amount of samples specified in "GI vs. AA balance" by a given factor to use them for direct light sampling. 


  • Total amount of samples is dependent on Light samples multiplier and GI vs. AA balance values. 
  • If Light samples multiplier is set to 1 and GI vs. AA balance is set to 16, this means that 16 GI samples and 16 direct light samples will be used for each pixel per pass. 
  • If Light samples multiplier is set to 2 and GI vs. AA balance is set to 16, this means that 16 GI samples and 32 direct light samples will be used for each pixel per pass. 
  • In some situations it makes sense to reduce one of these values and increase the second one, or even to reduce both. Typically, there is no need to increase GI vs. AA balance above 64 and Light samples multiplier above 4.
  • GI vs. AA balance should never be lowered below 2. 


The default value of 2 should work well in most cases, but sometimes it should be increased if there is more noise in direct light areas than in GI areas.


See: How can I tell whether noise comes from direct or indirect light? (3ds MaxC4D)


Light Samples Multiplier works in correlation with GI vs. AA balance (3ds Max | C4D).




Examples


Default settings

GI vs. AA balance = 16

LSM = 2

16 passes

Render time: 09:03


16 samples are used for GI and 16 x 2 = 32 samples are used for direct light. These are the default settings of Corona Renderer, which offer good balance between GI and direct light quality. They will work fine in most interior and exterior scenes.


(click to enlarge)


Direct lighting pass:

(click to enlarge)


Global illumination pass:

(click to enlarge)



Lowered LSM

GI vs. AA balance = 16

LSM = 1

16 passes

Render time: 08:15


The same number of samples (16) is used for both GI and direct light. Note that the quality of GI the GI pass remains the same as when using the default settings, but the quality of the direct lighting pass is lower. Render time is also slightly lower. 


(click to enlarge)


Direct lighting pass:

(click to enlarge)


Global illumination pass:

(click to enlarge)



Lowered GI vs. AA balance and LSM

GI vs. AA = 4

LSM = 1

16 passes

Render time: 02:47


The same number of samples (4) is used for GI and for direct light. Note that the overall quality of the image is much worse than with the default settings, even though the number of rendered passes is the same (16). Render time is much lower.


(click to enlarge)


Direct light pass:

(click to enlarge)


Global illumination pass:

(click to enlarge)



Increased GI vs. AA balance, lowered LSM

GI vs. AA balance = 64

LSM = 0,25

16 passes

Render time: 24:25


64 samples are used for GI and 64 x 0,25 = 16 samples are used for direct light. When compared to the default settings example, it can be seen that the GI pass has higher quality (at the cost of render time), and direct lighting pass has lower quality. 


(click to enlarge)


Direct light pass:

(click to enlarge)


GI pass:

(click to enlarge)



Increased LSM

GI vs. AA = 16

LSM = 4


The default value of 16 samples is used for GI and 16 x 4 = 64 samples are used for direct light. After comparing, it can be seen that the direct lighting pass has higher quality than the indirect lighting pass. 


(click to enlarge)


Direct light pass:

(click to enlarge)


GI pass:

(click to enlarge)