• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
jerrycao_1985

How does fixed pipeline handle shading?

2 posts in this topic

Hi all

I want to ask something about shading on fixed pipe.

The first one is about D3DSHADE_GOURAUD for the shademodel.

According to my understanding , shading is done in vertex processing before rasterization.
And I checked it with PIX , it turned out that no normal is passed onto pixel processing, which proves my point further.
Diffuse and specular color are interpolated during rasterization.
There is no such thing as per pixel lighting in fixed pipe at all.
Is that correct??

And the second one really confused me.
If color is computed in vertex processing, how does sphere map work in fixed pipe??
There is no normal or any direction passed onto pixel processing.
From the result , I can tell that it's not per pixel reflection.

So how does sampling works , in vertex processing??

thanks
0

Share this post


Link to post
Share on other sites
1) Correct, FF assigns colours (for lighting etc) per vertex whereupon fragments recieve a colour interpolated from the 3 vertices that make up the fragment's parent triangle.

2) The fidelity of the shading is coupled to the tessellation of the object being rendered. For a sphere, like any geometry, the higher the tessellation, the higher the fidelity of the lighting.

Of course, if the tessellation is low enough then lighting details will be missed completely or, perhaps even worse, rendered completely wrong. Imagine a large quad with a light of some sort near one of the vertices but that attenuates such that the other vertices are well out of reach of said light. The two triangles that make up that quad will have this vertex lit but as the shading occurs at the vertex level, the lighting will be completely off as the fragments will interpolated between this lit vertex and the two unlit vertices, resulting in a shaded colour that is disproportionally biased towards this lit vertex, even for fragments far out of reach of the light's radius. Per-pixel lighting (or light map texturing) avoids these interpolation errors.
1

Share this post


Link to post
Share on other sites
Fixed pipeline refers to a system where the vertex transformation, lighting and raster output computation are implemented as fixed (as opposed to programmable) hardware units for performance.

You can't run programmable logic in the "pixel shader" stage of a fixed system (the texture blending cascade in D3D), so you can't evaluate lighting approximations very effectively after the vertex processing. D3D9-era hardware does support dot product operation in the cascade, so you can emulate simple per-pixel lighting using normal map textures.

As for your second question, the fixed pipeline has a configurable (again, as opposed to fully programmable) texture coordinate generation logic that can generate texture coordinates for sphere mapping based on the incoming normals.

Remember that the vertex formats were also somewhat fixed back then, and the hardware "knew" what was the purpose of the normal element in the vertices. Today's hardware doesn't care at all about most of the semantics of a vertex structure; it is the responsibility of the shader author to give meaning to the all of the data. In modern hardware (or more specifically drivers), the fixed pipeline is internally implemented as programmable shaders that happen to have the same inputs and outputs that the fixed hardware used to have. Edited by Nik02
1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0