Frederic BOUVIER writes: > I discovered that only textures with an alpha channel are glowing > at night, and only when the c172 is in the view. Try the 4th view ( > free tower view ) and the magic fdm. When the 172 is viewed, trees > around are emitting light but when you move to clip it away, trees > stop shining. > > I modified my tower-hexa-2.rgb texture to remove the alpha channel > ( export to bmp and reimport ) and the tower stopped glowing.
OK, here's how plib sets up the states in src/ssg/ssgLoadAC.cxx. In AC3D format, textures and materials are separate: each object in a model can have only one texture, but it can use a different material for each surface. Each materials is defined with a line like this near the top of the file: MATERIAL "NoName" rgb 1 1 1 amb 1 1 1 emis 0 0 0 spec 0 0 0 shi 72 trans 0 The static get_state function actually builds the ssgState for each part of the model. It immediately sets the specular, emissive, and shininess properties directly from the parameters in the line (but they have no apparent effect in FlightGear). Next, it enables colour material with GL_AMBIENT_AND_DIFFUSE, together with lighting and smooth shading. If there is a texture defined, it then sets GL_TEXTURE_2D. Finally, it checks the alpha value (1.0 - transparency), and if it is less than 1 *or* the texture file has an alpha channel, it disables GL_ALPHA_TEST and enables GL_BLEND. The rgb value is copied to the vertex table for each of the vertices. So what's the interaction? Frederic identified the difference between a texture with and without an alpha channel. Why does enabling GL_BLEND seem to have this effect? In any case, I also have alpha channels in the textures for a couple of the buildings, and they don't start glowing unless the C172 is visible as well. Here's a different possibility -- the C172 has one texture with an alpha channel (which would cause GL_BLEND to be enabled), and one without (which would cause GL_BLEND to be disabled). Could that be the culprit? All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
