PDA

View Full Version : True or False?

dvwood
01-09-2009, 05:43 AM
Which of the following is true ?
A. in OpenGL polygons have to be convex (outside angle at each corner is >180 deg)
B. the face normal of a primitive is used for texturing
C. each texture coordinate is multiplied with the GL_MODELVIEW matrix automatically
D. back face culling is a way to increase rendering performance
E. lighting calculations are only done for vertices
F. the front and back face of a primitive is defined by its normal

Hey guys, need help again...
I am 110% that these are true: A. and D. but i am not sure about the rest. Can anyone help?

Groovounet
01-09-2009, 08:10 AM
A: true, but that such a pointless one because you don't want to use polygon anyway.
B: "usually" false but I sure it's quite easy to find an idea that could evolved the face normal in texture ... hum normal mapping? well it's more about the vertex normal.
C: false, it's multiplied by the texture matrix in the fixed pipeline ... and nothing automatic with the programmable pipeline!
D: true ......
E: false ... but one again it's depend! Could be done per vertex, per fragment, per pixel with the programmable pipeline. What's the meaning of lighting? Lightmap is a nice way for lighting and it's done per ... well nonsense.
F: false, it's defined by the vertex order.

Looks like one of this stupid and nonsense questions given by some employers. Without context, without any thinking to do ... I just hate those!!!

dvwood
01-09-2009, 08:21 AM
Thank you for the answers, they are much appreciated. Yes, well this is actually for a test.

k_szczech
01-09-2009, 08:28 AM
Groovounet - glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_REFLECTION_MAP_NV) for environment cube mapping :)

E - In this test I'd answer "True", but in reality I do lighting per-pixel, not per-vertex.

Groovounet
01-09-2009, 09:17 AM
You got the point k_szczech ... those cheaty things turn out more in "what I'm supposed to answer" raiser than "thinking".

My "favorite" onces. C or C++ tests! "What's this crappy code is supposed to do?" Well, I don't want to know and spend any time reading awful code or finding answer that a machine will give me without any brain damage resulting from boring questions.