Not only do I know for a fact that HL2 is HL1 engine revampped, you can tell from everything thats been done and happened.

Some of the screenshots show lighting errors identical to those in HL1, the increase in models rather than brushes. These are all given Lod models so that the engine does less over distance.

Also the compatibility issues of using the same file formats and compile tools to compile maps, the need for increased specs to run it.

The simplicity of the structures in the game, all made to look complex because of bump mapped surfaces, just like the models.

Need I go on?

Look at Tenebrae or whatever, If you can do that to the Q1 engine, then thats what HL2 is. Some of the tenebrae pictures look like Doom 3! And the coders for HL/HL2 are professional so they work out ways to make better looking environments, the inclusion of a multi lighting environment of prerendered and real time lighting also contributes to the faster speeds compared to Doom 3.

According to the mapper I spoke with, HL2 is pretty much HL1 with 12 dll files added to it... the dll files must be pretty mass.

Gravity is the amount of cheese that is holding the planet together.

Humans are actually splinters from sporks that mutated in a pile of twinkees.

The number 8 really doesn't exist.

Your credit card number should be given to complete strangers, along with any other identification.

And Gollum is the quickest and most prolific mapper the community has ever known...

? posted by Gwil

Is the mapper an official valve source though? TBH i'm just gonna play wait and see until the game is actually released

He supposedly talks to a 'Bloodlines' mapper (that other Vampire game using the HL2 engine), but it's been stated before that Source was built from the ground up (perhaps they stole some HL code though- this website was made from the ground up, but of course there are a fair few chunks of old code in it and it's built in a similar fashion!)