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Forum Index : Microcontroller and PC projects : sort of relevant..

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panky

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Joined: 02/10/2012
Location: Australia
Posts: 1114
Posted: 06:41am 16 Oct 2020
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  JoOngle said  Hardware support is the secret.

.....the CMM2 doesn't have real hardware sprites, it has "coded" sprites, that doesn't even function the same way as real hardware sprites do.

Real hardware sprites doesn't affect the main graphics memory in the slightest, it doesn't leave any trails of graphics OR scroll when the main memory scrolls or changes, because it's an hardware overlay.


.... but the CMM2 sprites aren't hardware sprites, so they are not "permanently" displayed on the screen regardless of the background, and they're "destructive" which means you need to copy the background to a page memory, place sprite, copy memory back to background and then place the new sprite position. Hardware sprites doesn't work that way, they are totally independent of the background and will not touch anything at all.



Jo,

In the CMM2, if you use colour depth 12, you do have the functionality of two independent display pages in that both memory areas are independent. Ie. writing to page 1 does not change anything on page 0 and vica versa. It is only at actual display time that the LTDC (hardware in the 734 chip) merges the pixel data from both pages, applying whatever transparency that was specified for the relevent pixels. The data in either page is not altered thus you can change or move the background on page 0 or any sprites on page 1 completely independent of the other.

You are absolutely correct in that if you are using sprites on page 1 for example, you need to manage collisions where they interact with other sprites and the movement of sprites is a read,backup,write,restore sequence (ie. software) but that is independent of the background on page 0.

So I guess you could say the CMM2 is sort of half way there!    


Doug.
... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it!
 
JoOngle
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Joined: 25/07/2020
Location: Sweden
Posts: 82
Posted: 07:23pm 16 Oct 2020
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Thanks for the kind update @Dough! I'll check that out.  
 
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