#228 part_color ignores alpha component

[Anonymous]

Using Gem 0.93.3 on Windows 7 32bit.

I noticed that when using a part_color, the 4th value (alpha component) is ignored. I looked at the code, and I think it is line 56 of part_color.cpp. When rendering, the color is not passed into the function.

[IOhannes m zmölnig]

afaict, this is a limitation of the "particle API" used by Gem.

while the pColor() function (as used in part_color.cpp:56) has indeed an "alpha" value, this is only a scalar, and not part of the 3D(sic! there's now 4th dimension for the alpha) space that forms a domain.

[Anonymous]

Sorry, not sure I understand you. Surely if the line changed from this:

pColorD(1.0f, PDLine, m_color1[0], m_color1[1], m_color1[2], m_color2[0], m_color2[1], m_color2[2]);

to this:

pColorD(m_color1[3], PDLine, m_color1[0], m_color1[1], m_color1[2], m_color2[0], m_color2[1], m_color2[2]);

it would at least pay attention to the alpha value of color1?

[IOhannes m zmölnig]

Well yes.
the question is, whether this is actually useful behaviour...
e.g. using a linear domain between (1,0,0,0) and (1,1,0,1) will "interpolate" between red and yellow, but the alpha value will be fixed to 0.