[Bf-committers] Yafray export
Matthew H Plough
bf-committers@blender.org
Fri, 09 Jul 2004 16:02:54 -0400
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<P>Arne wrote:<BR>"I've got a question concerning the Yafray-export. In line 1069 of export_File.cpp the lamp->dist value is used for the power of the lamp. But why? The distance term is in my opinion irrelevant, lamp->energy should be used for this."</P>
<P>The distance term is not irrelevant, if you want to duplicate the intensity of Blender's lighting in Yafray. I can't tell you the exact formula because I don't have access to the code at the moment, but lamp->energy and lamp-distance interact to create a lighting intensity. </P>
<P>Arne wrote:<BR>"Of course the amount of energy also scales with the size of the scene, but the user could then figure out how much "wattage" he needs."</P>
<P>I disagree. Wattage is a relatively useless way of specifying how much light is emitted. It is a measure of the amount of energy (joules) used in a given amount of time (seconds). It is not a measure of luminance, irradiance, or other interpretation of lighting intensity. For example, a 25 watt incandescent bulb can barely be used for reading, while a 25 watt fluorescent is quite bright. Since joules coming off of a black body of a given size is so far from intuitive that it prohibits further discussion, I suggest using lumens or another measure. But that would require correlating the grid size with a real-life distance measurement, such as the meter. I don't see a problem with that from a usability standpoint, so long as that distance can be user-set.</P>
<P>Matt</P></BODY>