So,I'm using PhysX,and I was wondering,do I have to add a Nvidia intro/logo/anything because I'm using it in my demos?

https://developer.nvidia.com/content/physx-sdk-eula bullet point 6. At least, if that is the EULA that applies to you.

B. For Games, Demos, and Videos that incorporate the PHYSX SDK or portions thereof, the NVIDIA
logos must appear:

a. on the back cover of the instruction manual or similar placement in an electronic file for the purpose of acknowledgement/copyright/trademark notice;
b. on external packaging;
c. during opening marquee or credits with inclusion of “NVIDIA”;
d. must appear on title marketing feature list with a specific call-out of NVIDIA PHYSX Technology
e. on the credit screen; and
f. in the “About” or “Info” box menu items (or equivalent) of all Physics Games or Applications using any portion of the PHYSX SDK.

Ok,but don't they provide any links where I can download the material(the logos,etc)?

The logos are usually in the SDKs unless you have a submission process. If not in the SDK, you probably have to contact physxlicensing@nvidia.com

B. For Games, Demos, and Videos that incorporate the PHYSX SDK or portions thereof, the NVIDIA
logos must appear:

a. on the back cover of the instruction manual or similar placement in an electronic file for the purpose of acknowledgement/copyright/trademark notice;
b. on external packaging;
c. during opening marquee or credits with inclusion of “NVIDIA”;
d. must appear on title marketing feature list with a specific call-out of NVIDIA PHYSX Technology
e. on the credit screen; and
f. in the “About” or “Info” box menu items (or equivalent) of all Physics Games or Applications using any portion of the PHYSX SDK.

damn what a vulgar way of adversiting, I got no idea on this

if so this is a big minus for using physX for me

also this that nvidia not supports OpenCl larger than 1.1

is bad minus for them