• 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.

Archived

This topic is now archived and is closed to further replies.

TUna

Using Assembly to Plot a Pixel onto a DirectDraw Surface

6 posts in this topic

I'm having a bit of a problem putting a pixel on a DX surface with ASM. Here's a snippet of the code: inline void plotPixel(WORD *surfPtr, DWORD dwPitch, int X, int Y, int Red, int Green, int Blue) { WORD col = (WORD)RGBToColour(Red, Green, Blue); _asm { PUSH eax // Save current values PUSH ebx MOV eax, X MOV ebx, Y ADD eax, ebx // Add X and Y MOV ebx, dwPitch MUL ebx // Multiply the result by dwPitch ADD surfPtr, eax MOV bx, col // Shift the colour into BX MOV WORD PTR surfPtr, bx // Move the colour onto the surface POP ebx // Reset to old values POP eax } }; The surface has been locked, and I have got the pitch from the DDSURFACEDESC etc... The code works fine when I use normal C++ [surfPtr[X + Y * dwPitch] = (WORD)RGBToColour(Red, Green, Blue);] I presume its something to do with adding to the surf pointer and/or moving the colour onto the surface. Thanks Edited by - TUna on 2/10/00 10:58:30 PM
0

Share this post


Link to post
Share on other sites

You''re adding X and Y before you multiply
Y by the pitch.

Also, are you using a 16bpp surface? If so,
you need to multiply X by 2 (or shift it left
once) before you add it in.

Try this:

MOV eax, dwPitch
MUL Y
MOV ebx, X
SHL ebx, 1
ADD eax, ebx
MOV WORD PTR eax, col
0

Share this post


Link to post
Share on other sites
It doesn''t seem to like the MOV WORD PTR eax, col.
Here''s the error MSG: error C2421: PTR operator used with register in ''first operand''

Any ideas?
Thanks
0

Share this post


Link to post
Share on other sites

Oops, sorry...

Try this instead:

MOV eax, dwPitch
MUL Y
MOV ebx, X
SHL ebx, 1
ADD ebx, eax
MOV ax, col
MOV [word ptr ebx], ax
0

Share this post


Link to post
Share on other sites
Hey, if you want to give a little boost to your code, here are some things you may want to consider.

1) You do not need to do a PUSH EAX and PUSH EBX to preserve the registers as the compiler will do this for you (if you are using Visual C++).

2) I''m assuming that you are writing to a 16-bit surface because of your surfPtr being a WORD pointer, this means that you will need to intermix 16-bit and 32-bit code together which, if not done right will cause penalty stalls on the Pentium processors (ya it''s stupid, I know!).

3) If your writing one pixel at a time at a specific location, then this function is useful, BUT if you are writing a series of pixels to the screen at a time, then you should modify the algorithm to write 2 16-bit pixels at a time, this is twice as fast because the bus is 32-bits wide, so when you write just 16-bits your only using half the bandwidth.


Good luck.



~-------------------------------------------------------~
Fred Di Sano
System Programmer - Artech Studios (Ottawa.CA)
~-------------------------------------------------------~
0

Share this post


Link to post
Share on other sites
i think you could do this in C because in your function you use RGBToColour and this is probably longer to execute than the rest of the function
0

Share this post


Link to post
Share on other sites