I have seen a lot of confusion in different threads on how SSD bandwidth can impact graphics fidelity. So let's do it.
There are a lot of misconceptions like: SSD has nothing to do with better graphics, more bandwidth means more RAM per frame, it's useless, and so on.
TL;DR
Higher SSD bandwidth can give you much higher detail around the player while keeping RAM usage and RAM bandwidth exactly the same.
Now let's start.
I have a picture for you.
WTF is that?
It's a graphical approximation of two LoD systems: orange and blue.
The horizontal axis (x) is distance from the player (player being always at zero coordinates)
The vertical axis (y ) is asset quality (texture resolution and such) the closer we are to the player (at zero) the better the asset quality should become.
The blue LoD system has 2.66x worse assets close to the player but kind of a better ones farther from them.
The area below each graph represents the amount of memory that each system uses.
You can calculate it yourself if you want, but I will tell you that the area is exactly the same.
I.e. both systems will use exactly the same amount of RAM and RAM bandwidth,
On the bottom of the graph you can see two lines with dots at the end.
Each line represents the length of the curve for the same color graph.
As you can see it looks like the orange graph is 2x longer than blue one.
And it's indeed the case (1.9x longer) but what does it mean?
Let's think about it.
When player moves anywhere, what happens to the graph?
It moves right.
Why? Because when player moves anywhere (left, right, forward or backward) the LoD system needs to discard the closest data (to the player) and stream-in the newer one.
Player always needs to see the best LoD around.
In fact the closer the data is to the player the faster it becomes discarded. And long distance data stays almost the same for a pretty long time.
(when you pass a building in wilderness all its textures are not needed anymore, but the mountains on the horizon will stay the same)
So the length of the curve represents the amount of data that needs to be reloaded in each frame when the player moves somewhere.
In our blue vs orange systems we load 1.9x more data each time into the orange system and get 2.6x more details around the player.
Here we obviously sacrificed some "longer distance" details for that.
We can tweak the orange system and reduce details around the player to 2x, or even below 1.5x and then we will have enough RAM to fill the "farther" details whuch will be pretty close to the blue system.
Still overall picture will look much better than in the blue system.
Also, in real LoD systems the far details will change so slow that they will be probably never reloaded anyway. And the real curve length will be shorter for both systems thus increasing the difference even more.
Update: how things compare to no streaming
There are a lot of misconceptions like: SSD has nothing to do with better graphics, more bandwidth means more RAM per frame, it's useless, and so on.
TL;DR
Higher SSD bandwidth can give you much higher detail around the player while keeping RAM usage and RAM bandwidth exactly the same.
Now let's start.
I have a picture for you.
WTF is that?
It's a graphical approximation of two LoD systems: orange and blue.
The horizontal axis (x) is distance from the player (player being always at zero coordinates)
The vertical axis (y ) is asset quality (texture resolution and such) the closer we are to the player (at zero) the better the asset quality should become.
The blue LoD system has 2.66x worse assets close to the player but kind of a better ones farther from them.
The area below each graph represents the amount of memory that each system uses.
You can calculate it yourself if you want, but I will tell you that the area is exactly the same.
I.e. both systems will use exactly the same amount of RAM and RAM bandwidth,
On the bottom of the graph you can see two lines with dots at the end.
Each line represents the length of the curve for the same color graph.
As you can see it looks like the orange graph is 2x longer than blue one.
And it's indeed the case (1.9x longer) but what does it mean?
Let's think about it.
When player moves anywhere, what happens to the graph?
It moves right.
Why? Because when player moves anywhere (left, right, forward or backward) the LoD system needs to discard the closest data (to the player) and stream-in the newer one.
Player always needs to see the best LoD around.
In fact the closer the data is to the player the faster it becomes discarded. And long distance data stays almost the same for a pretty long time.
(when you pass a building in wilderness all its textures are not needed anymore, but the mountains on the horizon will stay the same)
So the length of the curve represents the amount of data that needs to be reloaded in each frame when the player moves somewhere.
In our blue vs orange systems we load 1.9x more data each time into the orange system and get 2.6x more details around the player.
Here we obviously sacrificed some "longer distance" details for that.
We can tweak the orange system and reduce details around the player to 2x, or even below 1.5x and then we will have enough RAM to fill the "farther" details whuch will be pretty close to the blue system.
Still overall picture will look much better than in the blue system.
Also, in real LoD systems the far details will change so slow that they will be probably never reloaded anyway. And the real curve length will be shorter for both systems thus increasing the difference even more.
Update: how things compare to no streaming
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