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Member Since 15 Sep 2003
Offline Last Active Jan 31 2015 08:55 AM

Posts I've Made

In Topic: Modeling Light Sources

31 January 2015 - 08:58 AM

Thanks.  I'm using Fresnel R in my specular to get the amount of light reflected.  For opaque objects, do you scale the diffuse result by (1-R) since that is the amount of light that enters to do "body reflectance" as real-time rendering calls it?  In Real-Time rendering, for their final modified Blinn-Phong equation, they do not multiply by (1-R).

In Topic: Radiance Question

20 December 2014 - 09:53 PM

Okay I got time to review the radiometry terms again.  In the figure below I have drawn a spherical light source.  Are my explanations correct?  Figure (a) was hard for me to reason about.  I found that I wanted to think of intensity as radiance, but that I had to consider all areas on the sphere-light can emits photons in the set of direction defined by w.





Now assuming the above is correct, going back to real-time graphics mode.  When we define a point light source that emits photons equally in every direction we specify its radiance magnitude, say I_0.  Even though we think of radiance as a ray of light, it is really a thin cone.  So when the ray hits a surface, the photons in the ray have "spread out" based in the inverse-square of the distance, so to compute the irradiance at the surface we do: E = I_0/d^2 in our shader to get the irradiance from the point light source.


Now we apply some BRDF to find the outgoing radiance that will reach the eye, call it O for outgoing.  So O is a ray leaving the surface and reaching the eye.  But shouldn't O be attenuated based on the distance of the lit surface point and the eye?  As the distance increases, the photons will again "spread out" and cause less stimulii to a sensor in the eye. 

In Topic: General Programmer Salary

29 October 2014 - 01:43 PM

What if (heaven forbid) the company folds, and I find myself looking for a new job? I will get low-balled by every company out there on the basis of my previous salary. In addition to that risk, I feel that they're essentially asking me to take a pay cut for the company, which wouldn't even be out of the question if I felt like it would be appreciated, but I don't think they see it that way. Lastly, we are a small company, but our overall costs run in the millions of dollars per year, and so even if the company is not doing well, I hardly think that a $15k salary bump for one employee is going to affect things very much.


First, I would just wait until you finish school.  Looking for a job and going to school won't be fun. 


Second, don't worry.  Every time I switched jobs in my lifetime, I've gotten a significant pay bump in doing so.  When you apply for the job, use market rates from salary.com and glassdoor.com in your area to determine what you should get based on your experience. 

In Topic: Slow shadowmap cascades generation

02 October 2014 - 06:10 PM

In an outdoor scene, the bounding sphere of my last cascade was so big it put a lot of stress on performance.  The subfrustum size grows very quickly with distance, and I was using bounding spheres to make the shadow maps stable under rotation.  So what I did was make my last cascade static so it doesn't support animated shadows. 

In Topic: DirectXMath Calling Convention

29 July 2014 - 10:35 AM

I also think the library is fine.  Although I did write some functions to do 3d math on the XMFLOAT variations when I just have to do a one line math operation and converting to XMVECTOR would be a little annoying.  The library probably does shine more if you have a lot of CPU calculations to do (collision detection) and software skinning, lots of ray/triangle intersections.