Jump to content
IGNORED

Object Processor and the object list


Cyprian

Recommended Posts

In JagDox we can read that the object list has to be created every VBL due to OP modify it. What is the reason of that "modification"?

 

https://www.mulle-kybernetik.com/jagdox/op.html

2.5   The object in the objectlist are *modified* by the OP. This means      that an object list is only good for one frame. You need to      continually refresh your object list each VBLANK.

By a modification I understand the process of reading a phrase from a memory and writing it modified back. It is two cycles per phrase. Am I correct?

 

 

Link to comment
Share on other sites

The OP itself updates the memory in the list. As it builds the display a scanline at a time it does some logic on members . Now this is vague memories from years ago , but a normal sprite will have a start Y and an end Y and a data pointer for the current Y. The OP will ignore it until the Y matches . I then think as long as its not the end Y the start Y gets updated and the data pointer will be updated to the next line down.

Link to comment
Share on other sites

The Object Processor works this way because it renders the screen one line at a time, not one object at a time.

So for each object, it needs to remember what has already been drawn, and what remains to be drawn.

If it didn't modify the object list, it would need extra memory for that, which is a problem since there is no hard limit on the number of objects per screen.

Edited by Zerosquare
  • Like 4
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...